Quote: "The majority of spam that still shows up in my inbox never has my actual email address in the "To" field."
It would certainly cut out a lot of spam to have the filter you suggest. The only problem is that most mailing lists just have the list name as the 'To' address to prevent people on the list harvesting every members email address. This includes mailing lists from legitimate sources such as ISP bulletins (e.g. notices of downtime), general notices from eBay or other online systems you are a member of, and any groups you subscribe to (e.g. any YahooGroups).
Of course, you could set up filters which allow these particular messages before the filter which deletes them but its extra work for you. You'll have to weigh up whether its worth it depending upon the amount of spam you receive. Personally, my bayesian filters do a fine job now I have trained them.
P.S. I am having a sale on assassinations at the moment and my rate has dropped to $5000.00 USD
