John Gardeniers is right, the speed increase from using a hosts file is pretty darned small. The one case where it could be significant is if the DNS server itself was significantly overloaded. Even the overhead from DNSSEC is pretty small, though it can kill DNS servers ;).
The one thing I know of for things that NEED to be in the hosts file are addresses that have to be resolvable even during DNS outages. The one case I can think of is the LDAP server if you're using pam-ldap for authentication. And even that isn't a good use-case since the LDAP service itself can be configured with an IP address instead of a host-name.
If you're doing something funky with the localhost subnet (127.0.0.0/8) where you're using those addresses and need to access them by name for some reason, then a hosts file is justified.
We consider hosts file usage bad practice except in very specific cases.