psychology - Why don't users want to see adverts relating to products/services they might be interested in?

As we all know, Google's content display network, as well as many other successful setups rely on delivering targeted adverts to users to increase the chances of adverts falling in front of the desired audience.

I can't quote or link to any specific examples, but I've read many, many, many complaints from users online that keep seeing adverts for things they've searched for.

From a user experience point of view, what is the reason for this? Common sense surely dictates that someone that searches for "buy baseball bats online" might have an interest in buying a baseball bat online - and to an extent, other products relating to baseball. Surely it's a good thing that they see adverts relevant to their interests?

Why would seeing adverts for baseball goods/products not be desired over something completely random like movie rental or new dishwashers?

Edit:

_{Given that this question has become quite popular, I'd just like to point out (for the record!), that I don't enjoy my browsing experience being disrupted by adverts either; in fact, most of the time I do not even notice them (or when I do, depending on the advert it can give me a negative impression of the brand in question).}

_{This point is out of the scope of the question, the question was specifically to do with why users seem to complain more over targeted ads, than untargeted - which I believe we have some extremely helpful and definitive answers to.}

Answer

Users generally do prefer targeted ads to untargeted ones, all other things being equal. However, there are other important factors which explain why user reaction is mostly negative overall:

• Users don't spend all their time purchasing goods on the internet - often they are doing different and completely unrelated tasks, sometimes at the same time. Most people spend a very low proportion of their online time on ecommerce websites, and even then most of the time they aren't looking to buy anything.


• Given this principle, users often prefer to see no adverts when they are not buying - an advert in a non-commercial context is intrusive and annoying - and this is especially noticeable when the adverts are relevant to something you were searching for earlier.


• Targeted advertising can feel "creepy", especially if it follows you around from site to site. It's a constant reminder that your browsing and search habits are being tracked by someone, and people's mental models of the internet generally conceive of their browsing experience as being relatively private. Even if the process is completely automated, the degree of intelligence required to display ads to you makes it seem like you're being watched.


• Often users reject specific adverts due to poor relevance or some other factor; they then don't want to see it again. For example, if your advert is trying to sell me a catching mitt because I've searched for a baseball bat, then that advert appearing again and again is annoying because I have mentally decided that it's irrelevant. Persistence is not necessarily a virtue in this case.