I’ve just installed a fantastic WordPress plug-in that conditionally displays ads, the conditions are set by the webmaster of course – it is that flexible and more.
I won’t bore you with the technical details, suffice it to say that if you are registered and logged-in, no ad will be displayed to you, unless you are reading an article which is older than 15 days old.
If you are a “regular visitor”, that means you have read at least 4 posts in the last 10 days, no ads will be displayed to you either, unless of course you are reading a post which is older than 15 days.
If you have come here from a search engine, Google typically, then ads will be displayed in your session. According to many sources, it is these people who come through search engines who are most likely to actually click on an ad link anyway, so why bother everyone else?