I use an ad blocker. I used to use it without a filter list and would manually block any ad I found intrusive (e.g. Flash ads, ads that pick words out of the page content and highlight them, animated image ads), but then it simply became too much work. The tipping point for switching to filter list was spending two hours trying to figure out how to block YouTube video ads.

I want to support the sites I browse, but ad networks that host intrusive ads give all ads a bad name. Even worse are the irresponsible ad networks that allow advertisers to execute JavaScript, embed PDFs, embed Java applets, or even embed an entire iframe with a URL of the advertiser's choosing.