getting a user base

Any chat app has to have a user base.  I'd never want to create my own user base though.  I've found it hugely inconvenient in the past transitioning between chat clients and found apps like Trillian fantastic for managing connectivity to the multiple servers.  

Similarly, tons of websites have started using what's called federated authentication to allow logging in with Google or Facebook accounts.  After a little research, I've decided to start with Google's user base using federated login to allow access to the shoutbox on my site.  I've been reading a bit about how to do this today and hope to have this working by the end of the month.