There are two major crimes of Flash ads on websites: sound and CPU usage. I thought we outgrew sound on web pages. Seriously- having a MIDI on a web page was circa 1996, and we stopped doing it because it was annoying, could cause problems with those nearby, an just in bad tasted. I don't want to mouse-over and hear a sound.
The bigger annoyance, though, is Flash ads on a laptop. Even when my laptop's plugged in, Flash runs Firefox's CPU usage up to 100% and the laptop gets hot. When it's not plugged in, the same thing happens, only now the battery drains in the event I want to whack a mole so I can get a "prize."
I installed the Flash blocker, but I'd websites respect my computer and just simpler ads.