A couple of months ago, I setup David Schweikert mailgraph scripts for all our incoming/outgoing mailservers. Since end of August, we've received 534278 mails, in addition we tagged 135893 as spam. That's like 1/5 of our incoming mails, are spam !!
Imagine the resources we waste on fighting spam.. Bandwidth, a dedicated server to scan, tag and store messages.
Over the same period of time, we've caught 1046 messages containing vira of some sort, and I've (through postfix header checks) REJECTED roughly 33000 messages.
It's a sad state of affairs.