After years of knocking Social Media, I dove in a couple months ago. That is probably one of the better things to do, get involved and get a "feel" for it.
For instance, how can I find out if this idea already been tried?
Quick search in your favorite SE should turn up the answer you may be seeking.
Does anyone have suggestions for resources for learning about the fundamentals, details, and philosophies of social networks?
I think there is as much content out there on Social Media as there is on SEO. There is an endless supply of research, surveys, polls, you name it. If you have an idea, don't wait much longer. At the rate new social media networks are appearing, it won't be long before the fad has peaked. Some say it has, others swear it hasn't. It is all relative to whom you're speaking with. :)
Oh, I do know one thing. If your service FAILs at fulfilling your users requirements, they will leave in a heartbeat and not look back. I've watched Twitter FAIL multiple times and I'll be damned if people don't leave in droves to go somewhere else. They'll go to PLURK or SocialMedian or some other SM site. They are becoming a dime a dozen. Your best option is to find the network that you feel best represents what you may want to do and join them. Get in the trenches and "feel it". Just be sure you have someone standing by to rescue you from the madness. ;)