What on earth is the difference? The US Govt has no more right or business to be in the banking business than they do in the farming business. (I'm not saying that can't do it or don't do it, I'm saying they shouldn't) If they guaranteed a loan, then they guaranteed it with taxpayer money. So I don't understand why you make a distinction. If they are bailing out, supporting or otherwise guaranteeing private business with my money or yours, even if it is for the 'greater good', then that is socialism in a nutshell. We've gotten used to a lot of it already, but that doesn't make it right or healthy.
The problem such 'deals' cause is really very simple. A corporation (and I'm only talking about corporations here) gets so big and so vital to the economy (or is at least perceived that way) that the government gets invested in the welfare of that corporation for 'economic reasons' that rise almost to the level of national security. When these corporations are preceived this way, then the corporation is free to have undue enfluence on the government which gets into the business of guaranteeing the security of corporations, not citizens. Before long, given the nature of the lobby system, campaign finance and even simple graft, it becomes impossible to tell the corporation from the government. They have a mutuallly beneficial relationship that does _nothing_ to enhance the governments only real job, which is protecting the liberty and security of its non-corporate citizens. Subsequently corporations enjoy liberty's and protections not enjoyed by the citizens. And that is wrong. Period. But we're pretty used to the idea now.