Have you ever noticed how you get outbid by someone with no feedback score...
A common trick by sellers is to make a false bid using a different user name. This is done so they can push you to bid higher.
So, how do you detect these bids? Well, it's usually rather simple.
First always check the bidders feedback. A zero score, or a list of purchases from 1 seller only is a good start. Also check other items that the seller has on offer. If you find the same buyer appearing in multiple places, then this may be a false bidder.
But, be careful before making any accusations, as these may also be legitimate buyers.
Contact Ebay if you suspect any foul play!