How is that disrespecting privacy? The billboard (so far) is not doing facial or license identification and recording that I drove by the sign at 2:23 on Monday at 63 mph.

The equivalent of this is showing gaming keyboard ads on ign.com, and bank ads on bloomberg.com. As long as same ads are shown to every visitor, this is no problem at all.

The people hate it when their actions on one site affect ads on completely unrelated sites. Real wold equvalent would be a salesman saying "I was passing by your house yesterday amd noticed you got a new bed.. Want to buy some bedsheets at a great price?". I think we agree this would be super creepy.

People can do that kind of online targeting without the need for privacy invasion. For example, if I wanted to target Apple users who probably have some disposable income, I'd buy an ad slot on John Gruber's blog. If I wanted to advertise to frequent travellers, I'd advertise on FlyerTalk. That kind of thing.