I believe that in the form stated it is more a metaphor for removing someone from the tender mercies of the law by posting a bond so that they don't have to sit in a cell until they are called to answer for their deeds. Of course, the financial "experts" behind the whole meltdown will never be called to answer for their deeds, so it all metaphorically falls apart. Rather like The Bailout.

This is enlightening: bale or bail

Wouldn't "Bale Out" be some sort of harvest-related activity, possibly taking place in WWII and involving steam tractors and Land Girls?

And I thought it would be taking blocks of hay out of the barn.

The phrase finder site is great! It is often a start for my research on the origins of phrases when I write that type of article, and often quoted as the source as many sources are mentioned on the pages.