What, you ask?
Pop-ups, I answer! POP-UPS! *tears out hair*
Yes, I'm sure they're necessary in some way. And that they serve a purpose. But I propose to you that the people who create the modern pop-up have NO SOULS. >.<
It's one thing to put enormous banners on the site itself, but banners are becoming insidious! Ones you can't close 'til they finish loading because they haven't got an "x" button (with the big DON'T LIKE POP-UP? CLOSE IT! mocking you), ones that won't let you right-click on the task-bar and close them, because the menu appears and disappears before you can select anything (that one makes me want to scream and hit things, and I often do), over and over again, some pages that give you not one, but TEN pop-ups at *once*, and every one of those brings FRIENDS. And some of these don't even load your destination page 'til they've had a chance to load, themselves. And sometimes, there are combinations.
But best of all, there are REDIRECTS. You know, those "So-and-so is an advertising supported service. Your destination page will appear shortly" things?
It's one thing to make me sit through those damned things, but keeping me on the ad for two full minutes is passing excessive and rapidly descending into Hell.