I get 100% deposit bonus on Fult Tilt but no promotions on pairing Full Tilt and Stars... Just why would I pair accounts instead of just having independent account on each site?
You misunderstood when you merge two accounts, your balance will be separately for each site, but only will be possible transfer funds between sites...
Couple of advantages.
First if you get mad at one site you can transfer your money to the other site.
The second is more practicle. If you wish to play a specific game at one site but you have no funds there you can transfer it from the other site instead of having to deposit to play the game you want to play.
Seems to just be an extra (small) benefit of having Stars and Tilt owned by the same parent company, being able to transfer funds between them. It's not much, but it's something.