Of course we already do this! Dig before you speak. :) However, we do not
filter our customer's email unless they turn on filtering. We tag
everything including SPF failures and customers can turn on rejection based
solely on SPF failures if they want, but that still doesn't help our users
who haven't turned on filtering. Our "admin|root|support|etc" filter
previously mentioned in this thread does. We do not have any ethical
problem filtering those messages since they are impersonating us. We
wouldn't presume that any other mail should be filtered unless a customer
requested for us to do so.
I applaud his move, and wish more groups did the same.
It would have been better if he had just installed SPF, and published DNS
records for his own domain, and rejected them based on that. Then other
people receiving forged emails with his domain would also be able to just
drop those emails.