No background process like mysql or pgsql. Thus helps me run on cheap ram. _IF_ it grows and gains traction, then switch to a better db, which until now has not happened. So I haven't thought about the "better db" i mentioned above.
I had a similar idea when I built RubyFlow - http://www.rubyflow.com/ - it's a Ruby community link site. Some people thought it was an amateur hack at the time.
However, RF does about 80,000 pageviews per month, has over 1000 registered users and gets about 10 posts a day, and SQLite hasn't proven a problem whatsoever. It's hardly a big project but it's bigger than 90% of small, part-time projects that use technologies that are more advanced than they really need.