My limited experience with "targeted" ads comes from Amazon as they have access to my extensive purchase history. However, they are completely useless to me. I'm not sure why the system tries to advertise the same product (or type of product) that I just purchased. This is the extent of the ads.

I would actually like to receive more relevant ads. "Hey, we saw that you recently purchased a trash can, check out these garbage bags." There are so many supportive or related products that would be relevant to things I've bought. It's a no-brainer. Yes, I know there are "related" and "customers who bought this..." on each product page. I'm talking about after the fact in the days and weeks that follow the purchase.

And how about the option to say "No thanks, I'm not interested in these types of products right now." or "I already have this."? Is this really a difficult thing to implement?

Maybe I'm missing something.