Not trying to be snarky
I highly doubt the average advertiser online cares if you return or not after the initial purchase. Their motivation is not to match you with something you want or will even like, but with something you will buy. It is therefore in their interests to use the targeting information to craft as manipulative an ad as possible for something your demographic can be tricked into purchasing.
That's why, when ABP fails, I always see half-naked swordswomen advertising yet another click-and-wait castle building "game". It's definitely not something that I would enjoy; it's a slot machine with virtual payouts that costs real money. If I payed $10 into it, would I be happy with myself the week after? Compared to e.g., a novel I might like, spend as much time on, but have a decent memory or experience that adds to my life.
If I thought advertisers would use my information to find me things that are useful or actually a good experience, I'd be more receptive to it. I'd still refuse because I hate all this data collecting stuff, and there's no way to get your information back out, but I would feel like it was an okay deal for people that opted into it.
(1) I dont want to be advertised to at all, if I want something - I will go looking.
(2) I dont want my browsing habits in the hands of third parties, they should be between me, the browser and the remote server. Its creepy.
(3) Targeted advertising doesn't work - having crossed the rubicon, invaded my privacy, tracked my habits and carefully curated the extensive data they have collected on me - they then advertise something to me that is almost, but not quite, exactly unlike anything I need or want to buy.
(BTW, 90% of the 'targeted' advertising isn't targeted at all, because limiting the number of people who see my ad based on my guess at their needs and preferences is just dumb. Its WAY better to advertise to everyone and let them sort it all out.)
Mode shifting. When I'm in "work mode" I don't want to see ads for my daughter's birthday gift shopping research, and vice versa, its kind of jarring and probably the near opposite of the "smooth personalized engagement" the advertisers were promised. Heck, if I'm not at work, and work is stressful, I don't wanna see anything about work when I'm not at work. Or if I'm going on vacation I don't need the distraction of vacation ads while I'm theoretically working.
Another jarring impact is related to the current sorta-anonymous way the internet presently works where what I looked for on ebay has very little to do with what I looked for on amazon so ads based solely on one or the other are going to be an epic fail. If you google for the term "uncanny valley" what I'm claiming is 2013 era state of the art targeted advertising is very near a local minima or whatever of the uncanny valley. Less personal and it wouldn't be so creepy, and more personal and it would actually be in at least some danger of occasionally being useful...
"things I might actually want" - things I might actually want At This Moment.
One fundamental problem is "targeted ads" usually mean target to one identity. If they were ever implemented as one identity AND simultaneous activity, well OK.
This is before we hit process issues. Don't spam me with car ads after I've signed the papers and driven away in something else. Yes I researched heavily online so you think I'd be a great advertising victim, but you're too late, the project is done. Why can't I see ads relevant to what I'm interested in Now as opposed to what I was interested in the past?
I buy a new video card every 2-3 years. Advertising would be almost useful for a couple weeks every hundred or so weeks. Most of the ads will be after I make a purchase, probably viewed at work where I'm theoretically not supposed to be doing home computing projects.