presumably someone tries to access your account with an obvious password and tries a few more until they get in and then change it.

I think I will change mine regularly if ebayy are that unsfe with their security.

Presumeably they can play the bidding game with themselves and make it look like a popular item.

I have been looking at one item for a few weeks and know the value it goes for generally. Bids always low enough to not quite get it - I can wait a bit - gain experience. Look for a seller withing driving distance maybe.