Does Blocking Negative Domain Names Make Sense?

MediaPost observes a growing trend for campaigns on the web:

Democratic political consultant Michael Bassik adds that many political campaigns are purchasing variations of their candidates' names. "It's common for campaigns to not only purchase up every permutation of their own campaign's name, but also negative URLs as well," said Democratic political consultant Michael Bassik. "That's exactly what George Bush did in 2004. He not only purchased his own positive names, but names that could be used against him."

The problem with this strategy is that it is impossible to come up with every negative domain name an opponent could use.  Perhaps you can protect against lame ones like "BushSucks," but what about "ClintonLies" -- where does it end?  Despite Bush's efforts, for example, About.com has a whole section of Anti-Bush sites.