That's a matter of the person bidding, not the scheme. I'm going to put a link to it in the about box, but a friend of mine coded a site
http://www.operationeagleeye.com. It's free- you can give donations- and it's well worth it. It aggregates the data from completed auctions, and you can see that a *lot* of people make out pretty good, but a lot of people lose money also. But it's all in why you're bidding, and understanding the process. Of the sites, Swoopo is best IMO because your bids are a rebate against the item. So if I spend $75 on bids on an item that's $90 and lose it, I can then purchase it for $15. The point is when you get to that magical ratio of price/2 spent in bids, you're better off losing it, then paying the extra. So the other part becomes don't bid on items you can't afford, and bid on items that you'd want, even if you had to spend full price.
A couple of real-life examples to let you see what I'm talking about.
1. I wanted a printer. The printer I wanted was $129 on amazon, but I saw it on Swoopo. The price on the printer was $99. I bid on it until the amount I spent in bids on the printer was $85. If I had *won*, I would have had to spend the $85 in bids, plus the $40 that the price was up to- a losing proposition. But I intentionally lost, and spent the extra $15 to get the printer. Still cheaper than Amazon, and I had what I wanted.
2. My son wanted the Tony Hawk game. I spent $45 on bids up front. I was willing to spend a bit more on bids because I wanted to get it, and the price they were selling for was full retail. But it ended up I didn't have to, because I got it for 11 bids, and $11 (estimated). So for $11 + $45, I purchased a $119 game. And it got even better, because with the bids that I had left over, I also won DJ Hero (which I wanted for myself) for approx $9, and Tekken 6 (which I wanted) for $4.44. So for $45 + $11 + $9 + $4.44 ($69.44 for those keeping count), I purchased about $280 worth of product.
It's people that go in wanting get rich schemes or not understanding the system or getting caught up in the bidding that lose out IMO... you have to approach it with a reasoned head, as with anything else.