Lots of compromised machines about. This week's mail spam has doubled and there are a lot more bad site hits.
I've blocked 1060 comcast IPs over the past couple of years, ranging from single hits to a few dozen per IP. My server is a small-time operation so this is very big. If I get time perhaps I'll see if they easily group into IP ranges - and then block those ranges.
On the other hand, BT here in the UK has been blocked on over 1160 IPs - but UK is my normal market. Maybe I should address them as well.