Open Thread: February 2010, part 2

The Open Thread posted at the be­gin­ning of the month has got­ten re­ally, re­ally big, so I’ve gone ahead and made an­other one. Post your new dis­cus­sions here!

This thread is for the dis­cus­sion of Less Wrong top­ics that have not ap­peared in re­cent posts. If a dis­cus­sion gets un­wieldy, cel­e­brate by turn­ing it into a top-level post.