I wondered about this as well.
CIO magazine recently had an article in the June 15th edition about Records Management That works.
What was very interesting was this quote:
"One of the issues is to make sure that the documents in their electronic form can be upgraded and transitioned from one technology to the next over decades," says GWU's Bonig. "
This implies the data MUST be transitioned between systems, (GWU must be a Microsoft University)in order to stay fully usable for future reference/lawsuits et al.
Why do they say this, because if you had been using Microsoft email programs since MS Mail, you would have had to translate or migrate or convert those emails to Exchange mail, Outlook 2000, 2003, 2007 and now Live.
You can not read older Exchange emails in Outlook 2007 unless they have been converted to a format which is acceptable to the new system.
Now, let's compare Domino mail. You can, and I do, access emails from R3(few companies were into Notes prior to R3 but even their emails are accessible) using my R8 client. From 15 years ago to now, it only takes one mail file, one client.
Lawyers should be pushing all their clients to use Domino for this reason if nothing else. The cost to maintain old hardware, backups and software is not justified, especially if you are a financial, insurance, government(cough cough The White House fiasco) or manufacturing entity.