I think they could have made it clearer, and changing up their FAQ didn't exactly make a great impression on a lot of users. That said; I think providing they tell users about this upfront, and don't waste their bandwidth on mobile connections etc (as they say they don't) - then I see no problem with this.

It's a way for users to get a VPN for "free". For most end-users they won't even notice/care about the odd HTTP request they're proxying. I think transparency may have been the issue here.