You know, I used to think that this didn't happen. I thought it was nonsense. I thought it was all fanboy stuff. Yet, I just recently read an article where Samsung was fined - they hired students to post bad experiences with HTC phones across various internet forums, and they spent nearly a million dollars doing so.
Citation here:
http://www.theverge.com/2013/10/24/5023658/samsung-fined-340000-for-posting-negative-htc-reviews
I think more or less there are some obvious posters both AMD and nvidia that are probably doing this. Here. There's one NV poster in particular, where if you do a google search for his user name you'll find something like 46,000 results across tons of forums of him doing nothing but trashing AMD. And then, there are posters on the CPU forum here with an obvious red bias, you have to wonder what's up with that. Probably the same crap. HAS to be. The loyalism cannot be explained with any type of rationality, and two of those guys were banned from the CPU forum. (thankfully). And it doesn't stop at this forum, i've seen it at others as well.
Basically, I think this is the new thing for tech companies to do. And it's F'ed up. Hire students in asia and europe to trash a competitor on various forums. If you look some of the posting histories or google search them, it becomes all to obvious. At some point, fanboyism has certain bounds - when it exceeds that and passes fanboy boundaries, stuff like what Samsung did is probably similar to what they're doing.