Its most likely shill bidding. I have about 15 ebay accounts (which I dont use anymore). Im a former powerseller and left ebay aka feebay along with most people this year. You cant make a living from it anymore, they ruined people this year with all their ridiculous changes. But its probably people bidding on their own items from different accounts because if nobody else bids on it, then they can at least leave themselves positive feedback, which raises their feedback percentage (because ebay has a new rule that if you get any negative feedbacks, your listings wont show up in search results and will be all the way at the bottom or a few pages back, even if theres only a few minutes left for the auction). The amount of visitors to craigslist is going to pass ebays soon because sellers like left ebay and sell there now since ebay treats its sellers so bad. You cant find bargains on ebay because they ran off most of the powersellers and small sellers with their new rules.
Examples: buyers can leave sellers negative feedback, but sellers cant leave negative fb for buyers, even if buyers dont pay, which has ran alot of sellers off since just 1 negative feedback greatly affects a sellers sales, and opens the door for buyers to scam sellers now.
Ebay allowed people to sell downloadable products until this year when the new CEO stepped in. They gave digital download sellers a few days notice before pulling the plug on them, so people who were making a living on ebay were shut down literally over night. Since digital downloads can be duplicated and sold over and over again, they made up a big portion of the items on ebay, so when they left it affected all sellers because when a person searches in google for an item, and comes across an ebay listing for a digital download, they might keep shopping on ebay after that which is good for all the other sellers. Now theres alot less listings in google, since theres alot less digital download listings, so theres alot less shoppers visiting ebay. Most of the digital sellers either left, or have to put their items on CD now and ship it, which caused them to raise prices to make up for extra money they have to spend on cds and packaging. Less customers means that people have to raise their prices, all sellers, to make up for the lost sales...then ebay raised their fees at the same time, so now sellers have to make up for extra fees too. They really shot themselves in the foot with this rule.