I used to sell a lot on evilbay and I found that quite often buyers would bid early on something, then get the idea in their minds that that item was theirs. Every time someone else would bid, they would come right back and raise the bid. By the time the item ended, it might sell for twice what it was really worth.
I think some people get possessive over items they bid on and get mad whenever someone else tries to take "their" item away from them. And so the bidding war starts.
To me, when I see something I want, I prefer to use a sniper program. I enter the highest price I'm willing to pay, and then forget about the auction. When it's over, if someone wanted it worse than I did, they own it. There'll usually be another one along shortly. And that way I don't have to worry about remembering to bid just before the auction ends at 2:30 Tuesday afternoon, or at 4:40 AM Thursday morning.