"All-in"...then walk away from the table?!?

I've been noticing this "move" alot on the televised tournaments. Player A goes all-in then disappears from sight! WTF?

I'd like to see a rule saying you must remain in your seat until action is complete on the round (ie, all-in gets called). This "going all-in, then running to hide in the crowd" junk is so bad for poker, IMO.

Does anyone else despise this chicken-bleep play?
Has anyone seen this during their own tournament play?