Google Talk is a special chat feature which is integrated into Gmail. It is a built-in messenger that shares characteristics with both closed and open messengers, but is also available as an external client like Pidgeon or Trillian. It uses the eXtensible Messaging and Presence Protocol (XMPP), also known as Jabber. While it operates on servers hosted by Google, it can interact with Jabber users outside their system. Jabber clients such as PSI or Pigeon work with Google Talk and organizations can even receive their own organization Jabber ID. This is done simply by specifying their SRV records with their DNS host to point toward Google. This gets you a personal Jabber server without the headaches.

Some legal services organization would prefer their messages never be scanned at all by an outside company, so that remains a benefit to continuing with an in-house Jabber server. Nevertheless, both personal Jabber servers and Google Talk transmit information across countless servers over the internet, so the level of risk is approximately the same for both services.

Links
http://googletalk.blogspot.com/