Reverse dns lookup

["Scott A. Zanke" <szanke directvinternet com>]

Hello,
I am currently running a personal RH 7.0 web/smtp/pop/ftp/ssh server on 
directvinternet.dsl with no reverse dns lookup.
I have a friend looking to run a server for business purposes and have been 
looking at dsl and T1 providers for him.
What is the disadvantages to a provider that doesn't do reverse dns lookup.
I'm fairly sure that business class providers will provide this service. It 
just got me thinking about what's lacking without it.

TIA,
Scott