Doesn't every well financed institution do similar things? I thought that was the substance of public relations: getting your side of the story out there. It even happens on a small scale e.g. Yelp reviews.
The sockpuppets tend to be more influential than drive-by commenters though. Some of them actually pretend to be respectable journalists and opinion-formers. The Church Committee in the 1970s blew the lid on this.
Operation Mockingbird is a famous historical example:
http://en.wikipedia.org/wiki/Operation_Mockingbird
The National Endowment for Democracy is more recent:
http://en.wikipedia.org/wiki/National_Endowment_for_Democrac...
Given history, it would take someone with more faith in open government than I have to believe there are no equivalent online operations today.