I was (luckily?) too poor to order mining rig at the time, and heck, my friends was gathering resources to actually set their own medium sized farm but gave it a pass since they did some research on ASICs but it's somewhat short-sighted to neglect mining coins because of high difficulty ratio and new technology coming in.
First of all, with good rig you can always mine silver and bronze for few days and just store your earnings on a stock/vault or just in pocket, if ship hit the fan, you can either panic and sell coins or take a risk and keep them. And I'm still talking about silver and bronze!
Secondly, even if a newer technology marches in it will take the spotlight and mining per se will open spots for mining to the new users. And again, if BTC difficulty is too high, why not try other ones? Of course, you can get in another scheme or strange coins like YAC but still, for the few days after some signs of upcoming events few not informed buyers will eventually buy those, especially if you will sell them for few cents lower than others. I mean come on! Why do I know market tricks and still don't own at least 100BTC? hahaha
I doubt they are a total scam. They aren't doing great by any means, but I honestly believe they will eventually fill all of their orders. I don't think they anticipated the response they got.
If the problem was the number of orders, they could have at any point stopped taking them. That's what any reputable business does. If you go to a store and they don't have what you want so you get a raincheck, they don't say "pay me now and we'll give it to you when we get it." They let you keep your money and pay AFTER they get it.
Pandora a gaming hand-held/unix emulator console was like that- they stopped taking orders when they did reach they factory quota and that was great marketing move. I still think Pandora was managed by honest and responsible guys, not only crazy and greedy geeks wanting to sell overpriced emulator.
Just to add on because I'm thinking about other cases where this happens... Amazon. If you pre-order or purchase something and they find that it isn't in stock, they will not charge you until the order has actually shipped (and at any point prior to actually being in the mail, you can cancel it).
What BFL did wasn't sell something. It wasn't allowing pre-orders either. What they did is secretly run a crowd sourcing campaign without telling everyone. Crowd sourcing fits this profile perfect (company needs money to develop items, so people donate in exchange for the finished items). It's shady, considering they never notified people that it was what they were getting into (at least not that I know of, based on responses from people).