There are many mechanics for advancement in Facebook gamest.  I am defining advancement as any persistent change in your game experience which makes some or all game areas easier.  In this post, though, I'm only going to address a particular kind of advancement mechanic because I've been thinking about it a lot.  That is the cooperative "building" mechanics that are often used in simulation games where you need to get your friends who are playing the game as well to help you finish a task or build an object in the game.  In general I like these mechanics because they encourage the social aspects of the game, but some games do them better than others.

I'm going to examine a bunch of games and how they handle these mechanics and what I like and don't like about each of them.  Then at the end I hope I can draw at least a couple of conclusions about them in general.

Farmville - Farmville has a couple of different building mechanics, but one is used overwhelmingly.  The building will require some number of several different resources, such as boards, nails, and bricks.  These resources are only available from other players as gifts.  Each player has a limited selection of these to give out, with the basic idea being that you should be asking for the items you need and each of your friends who can send you that item does until you have everything you need.  However, Farmville lets players get around that limitation very easily in two ways.  First, if you send an item you need to someone else, they are allowed to send you that same item even if it's not in their gift list.  Second, many times you can send out a call for a specific item and get it from people whether they have access or not.  So they've made it relatively easy for people to build items, and the primary restriction is that anyone can only send you one item at a time so it can take a while to build up what you need.

Review - It's mostly very basic and easy to grok, which should be expected from such a widely used app.  There's nothing clever, but with some effort anyone can make anything.

Frontierville - Very similar to Farmville at it's base.  A building takes some number of a few different resources.  Each player has access to two of those basic resources.  When a call goes out that you need resources for a building, you can choose which of your two resources to send to the asker.  There are many resources beyond those basic ones, though, and this is where it moves away from Farmville.  There are two mechanics for gaining non-basic resources.  The first is to have the player put out a general call for the resource and anyone can answer that call.  The answerer generally gets one of the asked for resource as well.  The second mechanic is to force the player to send individual requests for a resource to people in their friend's list.  Anyone who responds generates one of the resource for the player. These two mechanics are never for the same resource.

Review -  I love the general call where both players get the resource, although often there is a limit on how many people can replay.  Also, Frontierville has done a fairly good job of reusing some of those resources in multiple buildings so that you still want to answer the call even after the building is completed because you will get one that might be useful later.  I *hate* having to ask individual people for a resource, though.  It feels very "spammy" to me.

City of Wonders (old) - CoW has two mechanics for this; an old one which they are phasing out and a new one.  The way the old one worked was that the player would have to put up a post asking for people to help build a wonder.  Any player could click on that post and would get a decent cash bonus for helping to build it.  When enough friends had helped, the building would complete.

Review - There were two problems with this mechanic which compounded to hurt it.  The first was that any particular player could only help one on each wonder.  The second was that it often took 25 friends to build a wonder.  What this usually meant was that you would put up a new post for the wonder each day and try to cajole your friends into helping, nagging more and more as the number you needed got lower. Ugg.  Now, there was a loophole, however, which was that actually anyone on facebook could help construct the wonder, whether they were playing or not.  So in the forums a practice arose of posting the URL to your wonder and then everyone would click on each other's links to rapidly complete them.  The fact that this exists helps a lot, but only if you know about it.

City of Wonders (new) - All of the new wonders break the building task into pieces.  Each piece requires 4 people to help.  People can't help twice on the same piece, but can help on multiple pieces.  So even though it takes 12 or 16 helps to finish, they can all come from 4 people.

Review - This is much more friendly, but does require you to post the wonder multiple times to complete it.

Island God - There are two ways to build socially.  The first is by collecting resources from your friends.  Each player can send any of the three resources as gifts (one per player per day.)  And the player can make a post asking for a specific resource, and each friend that clicks the post gives the player one of that resource.  A friend can only click on a post once.  However, they can click once on each post you generate.  So if you are willing to send out the spam and have a friend who's willing to click on them all, you could get all the resources you need very rapidly.  The second method is similar to CoW (old).  A certain number of friends need to respond to a post you put up about the building.  Each can only respond once per building, but the number required is much smaller (the only one I've seen so far requires 5.)

Review - I kind of like the way resource collection works here.  In theory you just post each day about what you need and your friends respond.  Now, the fact that you can put out ten calls for nails and if a friend is willing to click them all gets you quick resources is kind of fun, but very spammy.  Still it means you need only one dedicated friend to help out.  The second method is much friendlier than CoW (old,) but is frustrating for me because not many of my friends are playing.  It would work well if the game gets more popular, though.  (I like it quite a bit.  Check it out!)

Summary - Cooperative building is one of the most fun elements of a social game.  You help out someone and you get a reward, and next time they'll probably help you out when you need it.  It builds community and helps your viral spread.  I do not believe, however, that it should be a friction point in your game.  There should obviously be some amount of challenge to it or it's not going to be as much fun, but making it take tremendous effort to achieve just makes people look for loopholes or avoid it altogether.  Save the serious friction for mechanics that aren't helping increase your DAUs.

Cooperative building can be a good place to monetize as well, but you want it to be a convenience purchase, not a necessary one.  You want a player to get 90% of the materials from friends and then have to decide if they want to wait another day or two to get the rest or just pay a minimal fee to get them now.  Frontierville does an excellent job of this.  The resources primarily cost a horseshoe or two each.  If you need 10 of them, you are unlikely to buy them, but when you've gotten 9 from friends and you can complete the building for just one horseshoe, that seems like an easy spend.  You could buy your way through in CoW (old) as well, but the cost was not per friend you were missing, it was a flat rate no matter how much was left to do.  That's much more painful.