At this stage, all we can bet upon is that Yahoo! instant messaging users will be able to chat with Google instant messaging users and vice-versa.
Microsoft has well walked away from buying out Yahoo! and the latter is now shaking hands with Google to collaborate on advertisements and interoperability of instant messaging networks. The companies have agreed on enabling interoperability between their respective instant messaging services; this is good news indeed for everyone -- users as well as developers of instant messaging services and applications.
Back in July 2006, Microsoft had announced landmark interoperability between its MSN messenger and Yahoo! Messenger for communication using text and voice. Users rejoiced about the interoperability, and could finally cross-communicate with their contacts on either instant messaging network.
With Yahoo! and Google, at this stage, all we can bet upon is that Yahoo! instant messaging users will be able to chat with Google instant messaging users and vice-versa as no further details are available from either company.
Yahoo! isn't the only one betting on interoperability of IM networks. Others like Meebo and eBuddy have done the same. Multi-network IM clients such as Trillian, Pidgin, Adium, or Digsby have served the purpose instead of running multiple IM clients. Using any of these, users can log on to multiple IM networks and use them simultaneously. Additionally, they can have different user names and passwords on each IM network.