Look, I'm as much of a repwhore as the next guy. That, and I'm bloody addicted to this site. That being said, I'm not reading a 20 page thesis and giving feedback on this site just for the upvotes.
Moreover, I prefer having a hardcopy when reviewing papers and the like so that I can write all over them. To do a proper review, I'd need to have a cup of coffee with you and yell at you for how wrong you are (I can't help it, I enjoy making other people cry).
The best thing you can do is find somebody knowledgeable about the topic that likes you (I know that's a hard proposition), hand them the paper, buy them coffee and probably something out of the bake case (I do love vanilla scones), and have them review it.
For the record, I had my thesis reviewed by a guy who was my best man. And that required a case of Guinness and pizza as an offering.