Interesting. Are you making money off your own facebook apps or by writing facebook apps for others?

Own. Given the speed with which you can test new ideas on the platform, i don't see why anyone would want to work on the cheap making apps for others.

What kind of apps? Games, mostly?

Games. Nothing else sells on facebook. Seriously, don't even try it :)

I'd love to hear more about your apps if you're comfortable with sharing the information.

Background: I've been working for a couple of months on a Facebook Page app called FanBldr.com and I've found it fairly difficult to operate.. it's hard to get feedback from users, Facebook is always updating the platform, and I'm not even sure what percentage of my users will upgrade to paying once I drop the paywall bomb. I find traditional web app development easier to manage and operate in the long term.

I am on hold for G+ or the next social platform. Facebook has decided to screw developers after they signed the Zynga deal that guarantees for them 30% of zynga's revenue (I won't be surprised if at some point facebook buys Zynga and closes the platform)

OAuth is all I use, i keep facebook integration to the absolute minimum. Working as an external website means it's completely portable. Minor changes are needed to turn it to a G+ application.

Also living off Facebook apps from 07. Biggest downside is having too much free time and working alone. Right now im studying for the MCAT

Would you mind giving some income information? Like a rough approximate or something? The viability of this strategy is something I'm very interested in.

It all depends on the number of users and the nature of your app. Typically 1-2% of users buy virtual goods, and eCPM from ads is pretty decent for US/Aus/EU/Ca audience. Aim for an addictive experience and the users will come.