This just came across my path and thought I would share.  Apparently there is an API (commandline) method of retrieving email from a user account.  This includes deleted email and can be retrieved from the beginning of time.    I have not played with this but if it works this could save a lot of money and help with security concerns.

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---------- Forwarded message ----------
Date: Wed, Apr 25, 2012 at 1:43 PM
Subject: Re: email discovery
Cc: Google Apps K12 Technical Forum <[log in to unmask]>

Regardless of having a backup/archive solution Google already keeps everything starting from account creation (including deleted content).  Through the audit API you can request an export of it.  Archiving products just make it far easier to access are analyze.