Yeh Jarse your not wrong and I understand what you say, but the downloading time of these unwanted banner-ads can be expensive. I probabley wouldnt winge so much if I was DSL'd or cabled, but ads increase my p!ssy dial-up ISP and satcom usage bill to around 200 bucks a month (or rather it used to).
Oh and Adsubtract doesnt actualy kill the ad so to speak. Its still there but invisible (run the browser cursor over it and it changes from an arrow to a hand, indicating a URL). Its the asociated gif or jpeg image (and thus the wasteful expensive time downloading it) it kills.