Verb - To go overboard and abuse whatever power you have (political or otherwise) to retaliate against an insignificant negative statement by someone with little to no influence, thus making a gigantic ass of yourself in the process.
Noun - A person who brownbacks
Note: Named after Gov. Sam Brownback who paid thousands to demand an apology from some high school kid who tweeted that "he sucked" to about 60 followers.
"I'm going to post something on facebook about how I think Obama is lame."
"Dude, I wouldn't do that"
"Why? What's he going to do, brownback me?"
"Well, if he does, make sure you wear one of my promotional t-shirts when they interview you. I wouldn't want a PR blunder like that to go to waste ^__^."