Kerberos V4 is certainly in wide use in lots of places, even here.
Kerberos V5, however, is needed to be even marginally tolerable for
WWW applications (V4 requires n^2 secret keys where n is the number of
administrative domains, and is thus not scalable.) Kerberos in
general is, IMHO, not sufficiently scalable for WWW purposes for
reasons I think I've blathered about before enough.
- Marc
-- Marc VanHeyningen mvanheyn@cs.indiana.edu MIME, RIPEM & HTTP spoken here