AppBrain offers to update app that marketplace does not
Were these pre-installed apps? You won't get market update notificatins for apps that are pre-installed, you have to go to the market and manually install any newer versions of the app and then you'll get future updates via the market.

The same thing happened with my Droid.  I heard about an update for Facebook (which came on my phone), but never saw an update in the market until I searched for it and manually installed the app.