But it seems that sites that using in-text advertising (http://en.wikipedia.org/wiki/In-text_advertising) are on the rise. Because in-text advertising uses JavaScript, it is much harder to avoid seeing these in-text ads. Of course you can always disable JavaScript to get rid of in-text ads, but the ubiquitous nature of AJAX these days makes it almost impossible to use the majority of the websites. There are other ways to block in-text advertising (e.g. redirect the traffic to the ads servers to 127.0.0.1 by modifying hosts file), but none is as easy as flipping an on/off switch like the case with flash blocker.

The main problem of most of in-text ads is that they are activated by mouse over event. While this might not be an issue for sites that use in-text ads sparsely, it certainly becomes annoying when in-text ads are densely populated on the page. You basically can not casually move your mouse without triggering the display of ads. Only a few in-text ads providers offer ways to delay the pop-up of in-text ads when mouse is hovered over. This partially eliminates the annoyance of triggering in-text ads accidentally. But I doubt that the majority of in-text ads providers are going to adopt this technique since it is not in their interests to not show ads under any circumstances.

I am sure that someone will come up with a clean solution to block in-text ads in the near future, but it would only be a matter of time before some other "ingenious" ways of advertising appear.