Auto backup?
Um, well, I'm afraid I'd have to put that in the same category as bloated runtime organization tools. Just as one can completely control the organization (or lack thereof) of one's libraries and content, one can certainly control one's backups.

In a word, "Ctrl+S". Alright, that's more than one word. Actually, it's not even a word at all. But whatever you call it, it's the same thing.

Some may say, "But, but...but... how am I supposed to remember to save? What if I forget?" Well, that can also be answered simply in a word: "Boo-hoo."
While one may argue "Boo-hoo" isn't exactly a word...
However, there are other answers, most of which are a little less... shall we say, less polite. ;-)

Software is unique in the fact that we can go back in time to a period before we screwed our whole scene up. We can't do that in real life.
So, we travel through our lives and do our best not to fisk it all up. We have to, because generally there is no going back to an uncorrupted version.

And while Poser may not exactly be real life, I think if we can remember not to screw ourselves up too badly, we can also remember to save from time to time. And to complete this unlikely analogy, while there are people who simply don't learn not to screw up their one shot on a purely linear timeline, and who in many cases deserve their ultimate fate as a result of their irresponsibility...
Well, if you can't remember to save, maybe your scene deserves to die, too. ;-)

Aside from that, think about what Poser does when it saves. It rewrites the entire file. A very large scene may take a good little while to write. And even if it's only 15 seconds, do you really want Poser interrupting your progress every few minutes to auto-back? That's the first option I'd turn off.
Then again, I tend to remember to save. ;-)