How does a USN destroyer get hit by a container ship?

While you were sleeping, a US Navy destroyer got T-boned by a container ship; 7 sailors are missing, a few are injured, and they’ve managed to limp the ship back to port in Yokosuka, Japan.

So how does a collision like this happen? Yes, it was night, but both ships have radar, and with it they can sense other giant ships for miles around. The destroyer in particular, I would think, should be very, VERY good at knowing what’s around it and when/whether something is approaching.

Any sailors care to speculate on who screwed up and how?

There is some discussion here:
http://boards.straightdope.com/sdmb/showthread.php?t=828857

Closed by request due to there being an active discussion elsewhere.