I think that some sellers get nervous that their item won't be 'bid up' to the $ that they want (was the start price considerably low?), so if there is no bidding activity and the item is getting close to ending they 'get in first' and end the listing. I feel this is wrong, if a seller is not willing to sell for .99 cents, they should not start bidding at .99 cents!

It also could be legit (not likely on 3 separte items, but I try to give people the benefit of the doubt), I once listed a 4-foot aquairum and accidently dropped it before the auction ended so I had to end the listing before anyone bid on it.