Quick question about secondary addresses

["Dan Lockwood" <dlockwood () shastacoe org>]

I'm in a debate with a guy over the use of 'ip address x.x.x.x s.s.s.s
secondary' on Cisco gear.  I seem to remember reading that the use of
secondary addresses is a bad idea, but I can't recall the details of
why.  Process switched?  Can anyone offer a resource or more specific
information?

Thanks,
Dan