Personally, I both see the appeal and I don't. On the one hand, it's never an inherently evil thing to use your money in order to make more money. If you have $1,200 for three PS4s and want to make a $200 profit off that $1,200, by all means do. But I also find that a lot of the people who buy into product launches with this intention look at everyone around them as idiots who they're doing some kind of favor. A co-worker of mine was borderline hysteric when I ran into him earlier today over the fact all three of the systems he was planning to sell will be arriving tomorrow morning but the Killzone bundle he bought for himself won't be arriving until the 19th.
When I told him that it seemed kind of fair that in exchange for re-selling those three launch day systems for $550, $475 and $600 respectively he'd have to wait another five days for his own system, "this is America and there's always a penalty for being stupid and lazy in this country. I'm doing those idiots a favor, they had months to pre-order and didn't." I said that's cool and all, but the fact remains you took three PS4s off the shelves that three people could have bought at retail price.
Again, I see his point in some respects and I don't begrudge him making money with his money (though there is that small tingle in the back of my head that says, "man, why were you so comfortable waiting for inFamous all this time and now you're jealous?") but I can't help but get over how most people I run into on- and off-line who do this feel entitled to having their cake and eating it too. Some folks I know straight up canceled their extra pre-orders only because the market in their area seemed uninterested in going above a $50 profit.