Most likely scammers that are offering, check thier feedback, look for irregularities i.e. majority of them being new users or having changed their name..
I mean if you made it 100% clear, that not every one would win, then I guess you can cancel their bids i think.
I mean its unbelievable the amount of times people dont/misread auction info, i have to end up putting it in multicoloured size 30 writing telling them things which they should have read in the first place.