I've known about the Firefox adblock plug-in for a long time, but have resisted installing it. For the most part, I think that sites I visit have a reasonable case for showing advertisements (to pay for the thing that I'm going to view or use). I don't mind that they make money. And, I don't mind getting ads that are related to what I'm doing, so it was sort of a win-win for everyone.
However that changed today... Over the past few weeks I've been poking around on my system when it would go slow. Of course, Outlook was frequently to blame. But there were times when I could not attribute the problem to Outlook and looking in my task manager, I found that it was Firefox that was using up the CPU -- 15 to 20% of it, even when I was doing nothing.
Some experimentation found that there were several adds running on different sites that were flash based and were eating away at my CPU.
So, I installed the plug in, restarted Firefox, and went to the pages that had the ads in question and easily blocked them. I'll continue to allow ads that aren't hungry consumers of my CPU (for the reasons I gave earlier), but nobody has the right to put an ad on my system that has a measurable impact on the performance. Ad writers, take this to note... Stop with the flashy, high load ads lest we block them all.