Dammit Magus.
Bruteforcing somebody's account is illegal. The crime/punishment sort of depends on where you live/where the account is located.
Are there just unlimited login attempts, or what?
I dunno, but I haven't reached a limit so far.
Here's how I do it:
First, I whip out the ole list of hacked email accounts.
Then I rummage through the person's messages looking for one that's from eBay.
This will have their eBay username inside it.
Next, I enter the username along with whatever password I used to get into their email.
If that doesn't work, I try every other password of theirs that I know (myspace, etc.)
Usually while doing this I learn more and more of their passwords, and I try them all.
I've done this twice so far, and both times I've got in fairly easily (THAT'S WHAT SHE SAID!)
UPDATE: I just OMGHAX'd somebody's iTunes account. Yay me!