One of the earlier mozilla betas (1.1? 1.0?) had a preference for disallowing any links to open new windows and I fell in love with the feature. Even after I upgraded the browser, the preference stuck on that machine, and I was disappointed to see it cut from future versions (I had no idea how to replicate it on other machines).
My reasons for not liking new windows are many, but in short: I don't like unexpected behavior that breaks my back button and reduces any organization I have set up. I have a middle mouse button I use to open in new tabs, which I use often while reading blogs. When I click a link on a blog without a tab keystroke or mouse modifier, I expect it to replace the window I'm viewing and dislike it when it pops a new window.
I'm a power user and am quite comfortable memorizing a few keystorkes, but I'd say casual or new users are just as confused by new windows popping up indiscriminately. I've watched family members new to the web surf and ask "where did that story go?" or "what is this? how do I get back to where I was?"
Well, this post at Blogzilla tells you how to suppress new windows with just a couple simple clicks. It's simple, powerful, and easy. Thanks for giving the user the ability to control this, mighty mozilla.