Full disclosure: My previous computer had firefox and adblock installed and I used it extensively. I am now using firefox without adblock. Adblock is a tool, and just like any tool, it has the potential to be use for good and evil. A sledge hammer is a tool as well, but it is challenging to use constructively for a task like hanging pictures on your wall. If you are using it to make a site useable (your definition: stop viruses or flash ads or music ads) you are doing one or more of four things: Using the program ineffectively (looking at and blocking ads one at a time) (ethically grey, but I won't fault you) Using the program to block huge swaths of ads (sledge hammer approach) (evil, or at best, fighting evil with evil) Visiting websites that you should be writing off. Not purchasing the subscription from the site that removes ads. I don't think there is a fifth option, but perhaps the modern users can clue me in? Personally, the only site, on the entire internet, that I visit that has annoying ads is Ultimate-guitar.com, and they are pretty bad. Not evil though, because you can buy a cheap subscription to the site that gets rid of them, and it is such a powerful resource that I am willing to put up with them until I decide to pay for it.