My first thought - if your startup does take hold, you will NOT be losing sleep about in-house or out=house! Do remember that we're operating in an age of the '$100 Startup'! If you know you have a good idea - that you're solving a problem that no one else has solved very well yet - GO for it. Hire freelancers for the tasks you need immediately done, and trust your gut as you move confidently forward. Adjust as needed.

Actually, you're thinking too hard. If you venture off to micro-niche social sites, you'll probably hear lots of crickets and get lonely. Instead, work within the biggies like Twitter and LInkedIn. At Twitter, find your contacts via subject matter hashtags; on LInkedIn, join 'Groups' in your industry and begin participating. Be patient, and cultivate genuine connections.

You'd be surprised. Education, typically a very not-for-profit industry, is exploding in new ventures. And yes, utilizing open data is working for several startups. Check out GreatSchools.com (no affiliation) to see what they're doing with edu and data. If you're interested in this niche, ask questions like "What information (data) would parents want in choosing schools, colleges, scholarships, etc." Find an answer that needs answering....there ya go!