The trend that annoys me most right now is that image thumbnails never just point to the large image: instead they pop up some JS-based overlay that obscures the whole page. There are several issues with this:
* Quite often, for whatever reason, the overlay takes seconds to load (much longer than just loading the image)
* If the image takes long time to load, I cannot just put it in a background tab and continue browsing the page with the thumbnail while I wait.
* I cannot open several images simultaneously
* To close the overlay, I have to hunt down an 'x' button (for example pressing Esc usually does not work). The 'x' is likely camouflage dark grey in order to look good against the dark grey background, and placed creatively to make it difficult to find. Sometimes, the 'x' loads two seconds later than the overlay itself, to make sure the browsing experience becomes as frustrating as possible.
* Not uncommonly, the JS is so poorly coded that the overlay half-loads in my browser and cannot be closed at all without reloading the page. With JS disabled, trying to open the image might not work at all.
* If I react instinctively to the overlay by pressing backspace, it doesn't close the overlay; I get sent back to page before the page I was on.
At least the web designers who do this overlay crap are increasingly using JS for it, which is an infinite improvement over Flash.