Death threats get dished out online routinely, and few take them seriously — the Kathy Sierra row of last spring being the notable exception. But Dave Winer, the blog pioneer, may have chosen the wrong target over the weekend. In a Twitter sent while watching Hillary Clinton on TV, he wrote "Kill Hill Kill Hill." Webheads accustomed to Winer's dyspeptic logorrhea may dismiss such talk as the ranting of an addled mind. But the Secret Service, which protects Clinton as both the spouse of a former president and a presidential candidate herself, may view it with more jaundiced eyes. If agents pay Winer a visit, will he Twitter about that, too?