In a free, ideal capitalist exchange, it is not a case of one party benefiting at the others expense. It can't be, by definition, because then the free agent that is losing would not enter into the exchange. It is an exchange that both people benefit from. This is examined in more detail in the first couple of chapters of http://www.daviddfriedman.com/Academic/Price_Theory/PThy_ToC... (a textbook, not a blog post), but the short version is that due to the fact that different entities have different valuations on different items, free trade results in scenarios where both parties pay X-personal-valuation and receive X+N-personal-valuation, resulting in a profit. (The big failure people have in grasping this is missing the facts that valuations are personal, and valuations != money. After that, this logic flows simply and inexorably.)

Obviously not all exchanges are free and ideal, but both the cases you cite (Starbucks and EA), it's pretty close. I'd say 100% in the Starbucks case (you can get coffee from lots of places) and a little less so in EA's case due to the fact they have an IP monopoly on EA games (you can not obtain a Madden game from a non-EA source), but still, nobody's forcing you to buy Madden games either.

Swoopo is not like that. It is not a mutually-beneficial exchange between two parties; one party wins and numerous parties lose, with only one other party winning in theory (the auction "winner") and that still only at the discretion of Swoopo (if the "winner" is a plant, how would you tell?). Because the losing party entered into it freely and with reasonable knowledge of what is going on, I do not favor forcibly shutting it down either, as I can not imagine what such a law would look like anyhow. But we can still call a spade a spade; this is not like a free market exchange. This is a con game.

(The other possible out is that the auction losers are paying for an intangible feeling of fun or something, which is a valid thing to do if you choose not to judge people's value functions, but I suspect that a fair analysis would show that they are not really winning on this front either. Part of that analysis would be to show that Swoopo is the best way to obtain that feeling and I have to imagine a conventional casino is a better choice there for most people.)