Yes… Sure.
Any filtering technic is good:
To filter by DNS at the DNS level.
To filter by hostname… with the host file ( or host.deny file in some Linux Distribution )
To filter with squid guard.
Any technic is good, and have the possibility to make combination of these technics are even better.
My objective is ad filter, but you can enlarge this point of view in term of security…
Yes, I think to push a blacklist , to have the possibility to personalise this blacklist and use it at three different levels ( host, shorewall and squid ) is a very good thing.