Well, of course if you charge someone for a product and don't ship it, then you owe them their money back.
I'm not sure there's anything illegal about it if you give them their money back -- I'm pretty sure I've tried to buy something from a seller on Amazon, been charged, it turned out they were unable to fulfill, they refunded. It happens.
Now, if you run out of money and go out of business without giving everyone their money back -- that's still not exactly 'illegal', it's not in and of itself fraud. Companies go out of business with creditors all the time, almost any time anyone does go out of business they owe someone something (I mean, in a sense, that's what makes you go out of business!)
Most credit card processors will have problems with you if you don't ship a product within a certain time frame (3-4 days) within charging a credit card. I believe its part of the TOS.
And consumers are different than creditors. There are different laws that protect each.
I'm not sure there's anything illegal about it if you give them their money back -- I'm pretty sure I've tried to buy something from a seller on Amazon, been charged, it turned out they were unable to fulfill, they refunded. It happens.
Now, if you run out of money and go out of business without giving everyone their money back -- that's still not exactly 'illegal', it's not in and of itself fraud. Companies go out of business with creditors all the time, almost any time anyone does go out of business they owe someone something (I mean, in a sense, that's what makes you go out of business!)