I noticed when discussing about Exchange 2010, that many of us didn't noticed that for new feature about archiving and retention (much more visible) a new version of the dumpster is the key.
But with this new version of the dumpster we also get a better prevention against mistake in e-mail deletion's (prevention when Shift-delete) .
With this new dumpster, I encourage you to review your backup strategy. In fact the dumpster could also help you to avoid the need of a single item restore ...
Have a look : http://msexchangeteam.com/archive/2009/09/25/452632.aspx