http://en.wikipedia.org/wiki/Troll_(Internet)#Concern_troll
"Concern troll"
A concern troll is a false flag pseudonym created by a user whose actual point of view is opposed to the one that the user's sockpuppet claims to hold. The concern troll posts in web forums devoted to its declared point of view and attempts to sway the group's actions or opinions while claiming to share their goals, but with professed "concerns". The goal is to sow fear, uncertainty and doubt within the group.
For example, in 2006 Tad Furtado, a top staffer for then-Congressman Charlie Bass (R-NH), was caught posing as a "concerned" supporter of Bass's opponent, Democrat Paul Hodes, on several liberal New Hampshire blogs, using the pseudonyms "IndieNH" or "IndyNH." "IndyNH" expressed concern that Democrats might just be wasting their time or money on Hodes, because Bass was unbeatable.
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For example, James Wolcott in Vanity Fair accused a conservative New York Daily News columnist of "concern troll" behavior in his efforts to downplay the Mark Foley scandal. Wolcott links what he calls concern trolls to Saul Alinsky's "Do-Nothings," giving a long quote from Alinsky on the Do-Nothing's method and effects:
"These Do-Nothings profess a commitment to social change for ideals of justice, equality, and opportunity, and then abstain from and discourage all effective action for change. They are known by their brand, 'I agree with your ends but not your means.'"