I run Opera, which has a built-in content blocker. As a rule, I don't block ads because they're a revenue source for many sites and I consider them the cost of admission. If I consider the annoyance a fair exchange for the content then I'll accept the ads, and if I don't think the content is worth the ads then I won't use the site. I will disable particular ads on a case-by-case basis that I consider pathologically a…
That's actually completely understandable, because in many pop-up ads closing it triggers something else, or something that appears to be a close button actually isn't, and so on and so forth. I find these ads to be the most intrusive and annoying.