A lot of people have referred to Google Talk as "open source," but the source isn't open; it just happens to be using an open protocol called Jabber -- similar to how web browsers like Internet Explorer use open protocols called HTTP and HTML.

Google's supporters make a big deal about how you can use non-Google Jabber clients to connect to Google Talk, but somebody using a non-Google Jabber client doesn't benefit Google at all, so eventually they'll start adding new features...and those new features won't immediately work on other Jabber clients, even if Google publishes the standard...which brings us back to the early days of the browser wars, where Netscape would add non-standard (or not-yet-standard) features that didn't work on Mosaic or Lynx.

The real question people should be asking is "will my teenaged sister switch to Google Talk?" I bet the answer is no, because all her friends are still on Yahoo, and she thinks the hidden piggy emoticon* is the cutest thing ever.