Besides the "Wanna get away" ads, the company does a casting call and use's the talents a lot of employee's have. They get to have fun and it's cool to see your coworkers on tv.
I saw on the USAToday under the article about the year end profit of SWA a passenger posted how he can fly from ABQ to DEN cheaper than what UAL would charge for his bags to do the same thing, too funny.