Brand recognition is not the only purpose of advertising. Is BP trying to enhance brand recognition by bombarding us with TV commercials talking about what a bang-up job they're doing cleaning up the Gulf? Is Apple trying to enhance brand recognition by putting out videos of other smartphones dropping calls when held in a certain way? No -- damage control is another important purpose of advertising.

And considering these fora are one of the first links that comes up when you google "entourage edge", you're going to get a high proportion of people looking for more information after reading a blurb on one of those "iPad competitor" lists. If those people enter the forum and find a bunch of early adopters who are ambivalent or downright unhappy about the product -- especially when most popular review sites have been (imo unfairly) negative about the Edge -- they're less likely to buy the device. So it makes quite a bit of sense to plant employees in these fora posing as ordinary users but pushing the company line, rather than simply deleting negative comments by current owners which would alienate them and possibly cause trouble down the road.

(edit) I want to again emphasize that I'm not saying this is actually happening -- there is no evidence of a concerted campaign to do anything like this -- but I'm saying it's not implausible.