I started to hate stumbleupon recently. I have been a user for over a year and it was really interesting and useful most of the time, but recently it is spammed by professional websites (like an english ad-company stumbling every single page of their site), companies trying “viral ad campaigns” and plainly boring/disgustingly stupid stuff.
I am currently desperately looking for an alternative that is not overrun by professionals or companies.
Edit: Oh, and the biggest problem of stumbleupon at the moment: Emo-Poems. Yuck.