I'm up to about 1200 spam emails a day -- about 600 between the time I leave for work in the morning, and the time I get home, and another 600 between then and when I get up the next morning.
I've resisted filters because of the risk of missing valid emails.. as discussed in today's NYT.
It takes 15-20 minutes to scroll down through the inbox and delete the junk, each evening and each morning, before I can look at and respond to the valid emails (which amount to a couple a dozen each day). It's not quite prohibitive so far, but it's half an hour a day or more that I could be doing something more productive.