The mainstream media has picked up on astroturfing--fake blogs created by PR firms and political lobbyists designed to look like grassroots movements. And there are numerous examples of astroturfing, both in and out of politics
Friday's Boston Globe had a good story by Alan Wirzbicki about the concern political bloggers have over their sites being infiltrated by publicists posting as regular commentors. It's a legitimate gripe, too. Spam is annoying enough without it being from someone with an agenda that is diametrically opposed to your own.
Forget for a moment everything else associated with the astroturfing phenomenon; what ought to be of concern to PR firms is the black eye (or the deepening of the bruise) the practice gives our profession. If that's not enough, then think about the harm astroturfing will do to the building credibility of blogs as journalistic outlets (those that strive to be considered as such, at least).
The 2008 election will be a watershed event for new and social media. Now is the time to make sure its contributions count for something good and not become a case study in how bloggers 'gamed' the political process. That'll kill social media's credibility for good.