To help people undersand why and what of identicon, I hoisted up one of my comment to previous posts.
I originally came up with this idea to be used as an easy means of visually distinguishing multiple units of information, anything that can be reduced to bits. It's not just IPs but also people, places, and things.
IMHO, too much of the web what we read are textual or numeric information which are not easy to distinguish at a glance when they are jumbled up together. So I think adding visual identifiers will make the user experience much more enjoyable.
I think identicons have many use cases. One use is embedding them in wiki pages to identify authors. Another is using them in CRM to identify customers. I can go on and on. It's not just about IP addresses but information that tends to move in 'herds'.