Oh yes, it's hard. Reputation and ratings are abused by "brigades", groups of people who upvote all posts of other members and downvotes those of opponents. Eventually, it's a batlle of the most zealous and organized groups who are willing to put up the most time in this. These groups can be some volunteers on the Internet, but they can also be professionnal teams working on e-reputation/web-influence, and they know very well how to bypass the (mostly rudimentary) protections against astroturfing. It doesn't look like it, but it's a big business.