HOW IS IT A BUSINESS IF YOU CANT MAKE MONEY?
I tend to take a more traditional approach to considering my idea's as businesses. If there is no cut & dry method of monetization I don't waste anymore time on it.
Why not optimize on time and go with something that will work ( that can make money ), and save those hours spent on the "cool free thing" for later (aka your own time). It's just one less problem in the future.
At least in my opinion. I mean viaweb had idea of how they (you) were going to make money right?
For the same reason that I'm willing to fly to any large airport without knowing for sure that there will be a taxi waiting. There almost always is. And there almost always is a way to make money out of anything a lot of people find useful.