Just wanted to share this thought. I've used the new DH spam filter since it was released in beta, and I am very happy to note that it works extremely well.
I have set my filter at very agressive levels, and even so, it gets very few wrong picks.
But most notably, I can use the quarantine list to see that in the last 30 days, I've received about half as many spams than I did last month. I never expected spam to actually decrease, but it appears to happen...? Perhaps it's just a slow December and it will be back at full strength in January, we'll see. But it's an odd phenomenon -- less spam.
Try out DreamHost with a free WebID -- Prices, options