I've been fired by DH before.
This is a true story...
The day before I got fired I bought a hot dog from the hot dog vendor near the GTS office (the one accross from the Pizza Pizza, don't know if he's still there or not). Anyways, as my hot dog was cooking he's like three people I talked to this week lost their jobs, I think I'm cursed. He's like watch you're gonna get fired... less than 24hrs later...
It was pretty bizarre... not that I was surprised i got fired, i think i used up like two years worth of sick days and lates in six weeks. That and my habit of staying up until 5am kinda messes with your functionality at a day job.
Anyways in short, everyone I've known including myself that got fired got so because they were a drain on the businesses they were employed by.
I think that people who get fired see it coming... they know they've either lost interest or slacked off or got addicted to crack or world of warcraft or whatever.