I love tree-style tabs. It suits my [scatterbrained] working style to have 50+ tabs open at a time. I almost always middle-click links to put them in a new tab. This way, I can leave parent pages completely untouched while I go off on tangents, compare notes, etc. I eventually return to the page I started on and continue on my merry way.
Increasingly, links no longer point to discrete pages but DHTML elements that are meant to change the appearance of the parent page. They can't be opened in a new tab, and there's no reassurance that they won't mangle the page beyond recognition. Not only that, but they're hard to identify-- Generally their destination ends in an anchor tag (i.e. "#content"), but other than that they are indistinguishable from normal off-page links.
I propose that middle clicking these links opens an overlay that can be easily closed. This way, the damage can be undone, and the browsing experience can continue uninterrupted.