I found this article on online ads interesting considering I've recently started working for an agency thats main revenue stream is primarily from online ads.
To be honest I agree with the article, online ads are irritating and I never click on them. The only time I do is when they are well targetted (as on facebook). Atlhough I know this sort of targetting annoys some people as it means the ad companies have access to information you might not want them to know.
The short of it is for advertising to be effective it needs to be precise, tailored and suited to it's audience. Flinging ads everywhere just doesn't work.