> We currently have < 1% opt outs.

I have a feeling this may be because even "Close Buttons" on ads have a reputation for being untrustworthy.

I've drilled it into the heads of all of my not-so-computer-savvy relatives to NEVER click anything on any ads, even if it looks like a close button. They often aren't. (Telling mom and pop that clicking on 'em will give you viruses is very effective.)

Are your ads image-only, or can they be Flash, iframes, or include scripts?

Only text and/or static images with strict limited on how they are displayed so that they are not annoying or intrusive. No scripts, so no viruses, and no third party trackers or creepy stuff like that either.

Will those ads know that I bought/browsed for something several month ago and still try to sell me similar products that I no longer need?

The point is, I don't ever want to see one of your ads. Not even one. Whatever detection method you're using, I also want to block. Sorry if I sound like a prig, but I object in principle to advertising and the consumerism it seeks to instill.