Kinda sad, actually:
And not knowing too much about the nuts and bolts of pouring a foundation, this view is downright scary:
It's straight where the form meets the footer; I think this bowing is just from the 2x4s that are bracing it right now.
UPDATE: Mystery solved? With the help of Res4's engineering consultant (thanks Greg), we guess that the rain at the end of the last week added some pressure/moved the 2x4 braces on the uphill side of the foundation forms, causing the top of the forms to bow. Easy to fix by rebracing on Monday.