I've been curious about this same thing. I've noticed this happening more and more. According to Ebay however, they watch this closely and if they suspect it happening, they close them down as this goes against their rules. Yeah, right.

I think Eagle has given you the best advice. Bid on things at the very last minute. Lots of people who shop regularly on Ebay wait until the last minute so that no one will override their bid, and/or hopefully the owner won't do so in order to run the price up. If you suspect this, I would report it.

JJ