The majority of survey takers do so for personal monetary gain, not for charity. That's why practically all survey sites give points which can be converted into cash and gift cards. Now I'm not saying that eval.me will be unable to find users and companies to use its service (I'm positive it will), but my guess is that it will pale in comparison to traditional survey operations. But I do hope that I'm wrong and that eval.me becomes a great success.

There is a fine line and in my experience with a venture revolving around "portion to charity" model, it all comes down to one thing, your demographic users. I co-founded a startup (handled the tech) for an auction site where we promised HALF of every dollar we made would make to to charity. It was a risk to start and we knew that, but seeing as it hadn't been done, I can now say that at least I tried. It cost us so [insert frustrating word] much more to run the company, handle support, produce the product, market, mitigate fraud and deal with people trying to game the system than was worth it to even the charities involvement. We even took the steps to become a Commercial Fundraiser and be bonded in the states we operated to instill confidence in our users which ended up being a stark realization of why more companies dont do charitable acts, because theres so much in the way of doing good in this world when it comes to proper legal way of doing things.

All that said, about 8 months into the venture (and at the end of what we had left in the bank) I sent out this survey with the responses highlighted: http://9mtr.co/2v0S2X1C3G093t06273Y

As you can see, people responded with the best intention, but in the end, could care less. My point here is know your audience before you bank it all. We did our homework and found similar research that showed it might just work as well, but finding those people may be harder than you think, so don't underestimate the work involved. Regardless I wish you all the good luck and karma in the world to make this planet a better place.