But was it set up so that the person could participate in the dropbox affiliate program according to dropbox's affiliate ToS? I'm not saying right or wrong here, but I don't see the evil part yet on the part of the poster.

You run a site, you offer stuff to people to go out and market your product for you, they do so - as long as they didn't do it by creating fake accounts, what's the problem?

is affiliate marketing banned in googles ToS?