Thanks to the inclusion of pop-up blockers in all major browsers, pop-up advertising no longer poses as an annoyance to web surfers. In fact I not only block pop-ups, but block Flash by default as well. The side benefit of disabling these features is preserved bandwidth usage and generally much faster page load speed.
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.
