If you keep paying it because you like the house and want to continue to live there, being underwater doesn't mean anything.
Can you point to articles describing banks in 2008 calling in underwater mortgages? That makes no sense, since it'll only hurt them (the bank doesn't want to own your house, they want the income stream from the mortgage). Also, at least for all mortgages I've signed, there is no provision in the contract for the bank to do that as long as I keep paying.
