http://adblockplus.org/blog/anatomy-of-ads I've actually noticed this on some websites. The load times are significantly less in many cases.. on sites like Digg, which i use often, adblock probably cuts the load time in half
adblock has been known to completely knock a site down (as in not displaying in a browser) and even fuck up it's display. Had this happen to me a few times.
Its cause the flash adverts on some sites each so much CPU but ive never had a site display due to adblock on firefox
