Originally Posted by
MoreMilesPlease
Per the SW website, bolding mine:
http://www.southwest.com/travel_center/checkin.html
Because Southwest Airlines maintains an open-seating policy, general-boarding Customers may sit in any open or unclaimed seat. Customers holding boarding pass "A" will begin general boarding, followed by Customers with boarding pass "B," and then "C." General-boarding Customers who choose an emergency exit seat must meet all requirements set forth by the Federal Aviation Administration and Southwest Airlines.
I'm going to print that out and carry it in my wallet.
Of course, some seat hog will say that the seat isn't "unclaimed" after all; she has claimed it.