Other than pop-up blockers, I've not bothered with Ad block software. The sites I go to have very rarely use obnoxious adds.
Until today. Slate had an ad, for a movie called 28 I think, that was beyond obnoxious. I happened to be using Camino (I alternate between Camino and Firefox depending on my mood and how badly behaved FF has been recently), so I turned on their Ad Block feature. Sweet relief.
This is where the greatness of geeks comes in. Ads are the primary revenue source for web content providers. The success of web browsers is tied to the success of web content. If web browsers were produced by publicly traded companies, they'd never implement ad blocking. Enter the geeks. There are enough geek-controlled browsers to keep even IE honest.