1. A waste of 30 seconds of your life.
2. A completely uninteresting piece of news.
3. Coporate Bullshit.
Comes from deviantart, where notices known as "hot topics" are labelled as "H" in your messages. They're almost always completely uninteresting, lame promotions, and a total waste of time.
"You dragged me out here for this? Dude, you 1H'ed me!"
"Chechnya went 1H after a few years"
"Why is it that whenever I send a letter of complaint to some company, I get a load of 1H back?"