It comes down to intrusion in my personal mindspace. The ads I hate are the popups and the animations. The irritation of clearing popups is obvious enough. The irritation of distracting motion in the corner of one's eye is obvious enough too, when one stops to think about it. In my case, such animated adverts can help to trigger a migraine attack. Not nice.
Other web sites place ads in the middle of the page, with the content flowing round. I block those, too.
I'd like to suggest that the online advertising community get together to agree ethical and practical standards for the way they present their material.
Sadly, ethical advertising methods are something of an oxymoron at the moment. Hard sales techniques work, there seems no point in doing something different that won't. But think for a moment about where and when to do the hard closing. A good saleman doesn't wave promotional leaftets right in your face the moment you walk in the shop. That would make you pass right on by. No, the introductory manner is unobtrusive and relaxed. Only when you show an interest does the hard sell begin.
The same should be appied to web sites. It's common sense. A scattering of static, clickable adverts - great. Text links for those who have blocked images from other websites - great, too. Flashy, irritating nonsense leaves us passing right on by: save it for after we've followed the link.
Appropriateness of the material to the subject of the site is important, too. I have before likened Microsoft adverts on this website to General Motors advertisements in a Ford showroom - absurd, and to loyal customers surprisingly offensive.
These things could be got away with in the bad old days of anything goes. But that was then and this is now. Firefox has changed the rules of the game. Microsoft have had to add pop-up blocking to IE, with more me-too features due this Summer. The customer is king again and pop-ups are dead. Learning how to tactfully dissuade the likes of me from reflex ad-blocking is somthing which the online advertising community needs to embrace as a matter of urgency.
Hence my idea for ethical standards. If I saw a logo and banner proclaiming "Ethical Advertising Standard 1.0 compliant", I'd be more likely to go "Oh, yeah, now where's that Enable button?".
<fantasy>Down the line, a register of compliant sites could be hooked into the web browser, to automatically enable advertisements on compliant web sites.</silly_daydreamer>
IMHO the LXF website would be a great place to start. After all, what have you got to lose? (Oooh!)

Cheers,
Guy