I have a little over 8000 IP ranges, large and small (more than /16 to less than /24), listed as Always Ban (ie: server farms and aggressive DSL sub-ranges).
I further ban according to UA and other header fields which currently blocks about 4700 single IPs on a short-term (temporary) basis (that's just this year).
As to DSL ranges: acceptable countries 5300 and undesirable countries 2300.
This is obviously not the entire internet, even for ipv4. I add a few on a daily basis as new ones insinuate themselves (mostly due to DSL and servers contracting viruses!) but it's not unmanageable; certainly fewer than 40,000 ranges.