Internet Applications That Heal Themselves
This is such a good idea, I'm astonished no one has tried it before. It would be so great to not have to worry about updates or trying to fix corrupted files anymore. Also, a sophisticated-enough, self-healing, self-protecting computer program is probably the one thing that could completely stymie human spammers/hackers. (That just means they'd write programs to counter the programs, but oh well.)
And at the same time, this is a creepy development, because it's yet another concrete step toward creating programs that are, unambiguously, life forms.