Paid shills or "astroturfers" seem to be fairly common in other areas of endeavor - especially where there is money or political influence at stake - so I also wouldn't rule out the possibility of it also happening here. One way to unmask such individuals it to check their profiles to see how long they've been members of the forum. If their membership is in the order of a few weeks or less, and they havn't commented on other stories then it's quite possible they could be astroturfers.