I understand about the cost and it isn't for everyone, but we had 2 lawsuits that required us to produce every email from every manager and 3 departments (about 150 - 200 staff in 13 remote sites) containing X search strings.
We also have to preserve their PSTs in their original form at that time (create disk images if on local drives)
a HUGE PITA taking up the time of a dozen IT staff...
It wasn't long until the decision was made to go with centralized storage... there is always another lawsuit and discovery process.
