Guest IDs are fairly long but appear shortened (only the first four letters/digits) in the webclient for staffing. You can also give guests nicknames by editing the guest ID in the webclient.
The reason Guest IDs are long is in order to be in good compliance with XMPP (Jabber chat protocol) standards. This means that chat boxes have to do less negotiation with the server when a chat begins, which means that widget chats start up very quickly. And that means a better chat experience for your guests.