Apple-X.net has a post on how Google could overthrow AOL’s Instant Messenger with its own solution built around Jabber:
[Jabber] is an open-source messaging protocol that can do basically everything that AIM can do, except that no large companies have really endorsed it yet, so it hasn’t caught on that much (a mixed blessing). Like other ways of communicating online, like email and IRC, Jabber doesn’t strictly depend on a particular server. Most Jabber IDs are @jabber.org, but they don’t have to be.
An important feature of Joogle would have to be contact list portability and file transfer behind NAT, neither of which Jabber can really provide. Thus, Google could implement such features in their own client, which would also display a text ad in the contact list.
And it would work, even if users could choose to use a different Jabber client that didn’t display an ad and was even more customisable, for the same reason more AIM users don’t use Gaim.
What else would it need? Audio chats are important in modern IMing, so this is a must. Optimally, Joogle’s audio chats would be compatible with other VoIP software, like Skype and iChat. Also, since AIM maintains some public chatrooms, Google would be obligated to provide these as well. The difference? AIM’s are totally unmoderated, which allows bots to clog the rooms (there are often ten bots per user in these rooms). Google could moderate their own rooms, filtering out the constant droning of COME SEE MY WEBCAM, enabling users to carry on, at least, semi-intelligent conversations.
In the end, what would this accomplish? It’d hand the world of real-time messaging back to the public (there are dozens of different Jabber clients), end client incompatibility once and for all (assuming many people switched over to Jabber), and stop companies like AOL, which are arguably very evil, from monopolising a very fundamental ability and use of the internet.