In the past month, many if my regular sites have been flagged by Google for malware and when resolved it was all down to malicious software being served by their ad provider.
For the first time in years I visited Youtube on a freshly installed system without any addons installed, and it blew my mind how many ads there were. The main page had about 3 ads including a huge video ad in the middle. This was on a netbook and so the time it took for the ad to load was not appreciated. I loaded a music video and there was a video ad, a popup on the video, and that annoying frame around official music videos that show the next crappy pop star (in this case it was Nicki Minaj, and that was really unappreciated).
Some sites that I do visit ask me to turn it off and they so far have only served me very simple image ads or text ads which I don't really mind. It's when an ad starts playing animation and/or audio that I block them and sometimes just block the site itself completely.
You don't need to be intrusive to sell your product. It just annoys the end user. I don't remember a single flashy ads name, so that obviously does not work (in my case).