Ranked in these QuestionsQuestion Ranking
Pro Free & open source
Pro Blocks a wide selection of annoying ads
Video ads on YouTube, Facebook ads, flashy banners, pop-ups, pop-unders and much more.
Con Users automatically opted in to whitelist
AdBlock+ has an automatic whitelist when installed that allows certain advertisers through the blocking mechanism. The fact that these advertisers pay for this privilege makes this particular scenario rife with conflict of interest.
Con Uses too much RAM
AdBlock+ tends to use a lot of memory, which has been documented in many use cases as well as admitted by AdBlock themselves. Considering there are alternatives out there that can block ads successfully with half the RAM usage as AdBlock, one has to wonder why this is a problem specific to AdBock.