I accept fully that many sites, including some I run, need advertising to operate. My Wi-Fi Networking News site has Flash ads on it right now, for instance. But I am, unfortunately, finding that Flash ads are now often highly intrusive even on sites I trust. They cycle endlessly. They use visual effects to knock my eyeballs on the floor. They play audio without my permission (even more annoying when I'm already playing music in iTunes or using voice over IP via iChat AV or Skype).
Since Flash is not under my control, I've taken stronger action on my Mac and started using Flashblock, a simple Firefox plug-in that loads Flash content, but doesn't play it. Instead, Flashblock puts a replacement symbol in the spot occupied by the Flash object, that, when hovered over, changes to a play button. This approach puts me back in control of my attention, the sounds emanating from my Mac, and my Web browser.
If Flashblock catches on, it could become another reason for users of Internet Explorer (especially under Windows) to switch to Firefox, and it will probably reduce the response rate on Flash ads, thus moving advertisers to other mechanisms.
More generally, I'm troubled that advertising has become an arms race in which advertisers and consumers fight an ever-more-ridiculous war in which the advertisers feels empowered to violate a user's space - just as badly as those 1/8th-screen-blocking ads on television now during programs for the next program - while consumers feel no compunction with using technology to suppress advertising entirely.
In the long run, it doesn't benefit the advertiser to fight a war with the reader, however strong the return on a given style of intrusive and offensive advertising campaign is initially. It's important to remember that Google's billions come almost entirely from consistently formatted text advertisements. Advertisers are fighting for higher response rates than the gold standard of text ads, but they're fighting a losing war when surfers just turn them off.