Some will argue that salary caps are for budget balancing. Others will argue it means one team can't horde players (Unless you're the Yankees and you pay a tsk tsk fee every year).

From Swish Appeal:

When Swish Appeal spoke with Phoenix Mercury General Manager Ann Meyers-Drysdale in December she indicated that the team would be hard pressed to return it's entire 2009 championship roster due to financial constraints resulting from a $52,000 reduction in this year's salary cap.

We have since learned from league and team sources that the Mercury situation may be worse than originally reported.