Frankly, Roger, I think you'll find the spam situation has gotten so bad that if you do implement whitelisting on your role accounts, most users will nod their head in sympathy and wish they could too, especially if your return message says something like "I'm sorry to put you through the hassle, but we get so much spam now to this address, it's the only way we can make sure we find your message in all of the spam".
As I wrote to Chuq privately...
Well over 90% of the mail I get at my personal addresses is spam, but so far, I haven't seen a solution -- TMDA, Brightmail, SpamAssassin, whatever -- that seemed like any less a hassle than just deleting it.
