I like the corporate sponsor idea a lot. I think there are far more hikers out there than climbers although climbing gear is particularly pricey.
I had similar thoughts about asking for donations/charging a fee. I would be willing to contribute something but am skeptical we'd get enough people to matter. What do you do with the people that don't contribute? If you don't let them use the site, they'd most likely get mad and take away all of their contributions, so I think it would have to be voluntary.