msgraph - 11:08 pm on Nov 1, 2001 (gmt 0) Like the other day... [webmasterworld.com...]
Basically it is good to have a fail safe method and that is why many use both. Although it does not happen very often, some SE's add new IP's to their pool of robots a few times here and there. If you just base your cloaking on IP address alone then you may get caught with your pants down. :o
Like the other day...