I wouldn't mind reasonable ads
If all the advertisment did was show me something relevant and not track me. I could possibly accept tracking which site a click came from if it could not be matched to a purchase in any way. Or possibly if you could guarantee that it couldn't be tracked to a specific user. I don't necessarily mind the company I buy from knowing I've bought from them before. I don't want them knowing I clicked through from an advert on the guardian and letting that leak to the world. I've a reputation to maintain.
When I want to buy a lawnmower I'm happy for adverts showing lawnmowers. I'm not happy to still receive them three weeks after I bought one and am trying to buy a computer.
Have an advert for a SAP on the reg when I'm viewing stories about a disastrous oracle deployment is amusing, appropriate and may very well target a group of people that are interested and can purchase these services.
Having the same advert on YouTube if my kid is looking at some pointless video isn't useful to anyone.