We're thinking about adding it to our web app to reduce registration barrier, but it is going to be a bit of work to integrate into our account system, which will mean delaying other features.
For those who have implemented FC, has it helped convert a lot more of your site visitors, and has it helped growth a lot through the mini-feed messages of your users?
Any feedback or stats would be great..
Facebook Platform (and presumably Connect) is great for virality, but haphazardly slapping it onto something that wasn't designed for its strengths and weaknesses from the beginning nets you little. To use it properly, you have to design your app or site from the ground up around the platform. Otherwise you're wasting your time.
I haven't looked into connect much yet, but I'm guessing that if it allows for solid virality (invites, notifications, profile boxes, mini feed entries, etc.) people just haven't quite built the app that takes advantage of it yet. They're just adding it onto their blogs and social news sites and hoping, and unsurprisingly they're not getting much in return. Look through the portfolios of contractors who build Facebook apps and you'll see a lot of that. Some newspaper thinks they can just stick sports scores in a Facebook app and it will go viral. Those apps always have 12 active users.
So I guess my advice would be don't do it half-baked, or you won't get much from it. If you're going to integrate it, rework your entire product to use the viral hooks you get from it. It doesn't seem to be that much easier for a user than a streamlined signup process anyway.