Let's follow this line of reasoning. Suppose your image recognition software noticed something it thought was suspicious. What are you going to do about it? Have a human look at the backscatter picture? Do a pat-down? Either way, you're cutting down on the privacy invasion, but not eliminating it.

That's probably worthwhile, but I doubt it'll make people feel much better about the machines, and it'll piss off the people who will see it as backing down on airport security.