I came here to post this same thing, but I just started thinking about it. When was the last time FB went down like this and took a bunch of core functionality down with it? Has it ever happened? And how long are they down...30 mins? Is that 30 mins of downtime every few years really more damaging than that the (potential) value that integration with the graph API or FB Connect can bring? Yes, you look like an idiot to a few users, but maybe you have 100x as many users as you'd have otherwise. I think the real reason not to build your business on the FB API (or Twitter or whoever) is strategic, not because of potential downtime.