You know, it's bad enough that these fracking Twitter spammers are polluting my Twitter following count (inflating it from zero to three). I went and checked out the page that they redirect to and when I type into the address bar to navigate away from the page, I cannot! Observe the sequence:
I find it very annoying when I try to navigate away from something and then I'm caught with a "Wait! Don't go! We'll throw in this special offer!" If I take the time to hit Ctrl + L to get to the address bar (which doesn't work in IE8, btw, but I can't remember that program's shortcut sequence) then don't bug me with pop-ups. I'm sure I want to go, that's why I took the time to manually type in a URL.