Here's just a few numbers from our hosting servers to give you an idea of the scope of how bad a problem spam is:

Total messages handled for February: 2,835,385
Spam for February: 2,116,337 (75%)
Ham for February: 581,487

Total messages handled for March: 3,512,870
Spam for March: 2,026,343 (57%)
Ham for March: 510,425

Total messages handled for May: 2,598,944
Spam for May: 1,756,805 (68%)
Ham for May: 653,673

"Ham" is email that is marked for delivery. In general, some spams get through as ham, but very few hams get marked as spam.

Bottom line: Around 70% of the email that our mail server processes is marked as Spam. Yowsers.