Hmm. Looks like the upgrade to the latest version of Serendipity turned off the referrer tracking.
Silly software.
So I have no referrer data after 10/27.
I have renabled referrer tracking, so I should start seeing some data again (assuming that anyone is actually referring traffic to me.)
If you upgraded your Serendipity install recently, and you want referrer tracking, you might want to check your settings.