This morning I received a cool surprise email:

Hello AquamanBT,

Congratulations on your performance in last week's Sit & Go Leader Boards. A cash prize of $30.00 has been credited to your account.

It happens that I finished in the top-20 list of the $3-$5 division. This is pretty nice, since it's a 10% boost to my bankroll, without me being even aware of this Pokerstars promotion.