It really doesn't mean anything.  Petkovic should have won, exhibition match or not, but I'm guessing she didn't play as hard as she could while Clijsters did.

Sorry folks, Clijsters 4.0 is not coming to the tour.

For the people who think it should be Clijsters 3.0, you're wrong.  Here's how it breaks down:
Clijsters 1.0 - started at the beginning of her career until she injured her wrist.  Slam final appearances 4, slams won 0.
Clijsters 2.0 - started with her comeback and winning Indian Wells and Miami back to back.  Slam final appearances 1, slams won 1.
Clijsters 3.0 - started with her comeback after retiring and giving birth.  Slam final appearances 3, slams won 3.

Clijsters 2.0 and 3.0 did not lose to Serena or Venus.