This tutorial is for an outdated version of Google Chrome. Please refer to the updated version (05/31/12)
To disconnect your Google Account from the user’s current browsing session, first return to the Personal Stuff Options page by following steps 2 and 3 of this tutorial. At this point you will notice a Sign in section at the top of the page.
This section contains a link to Google Dashboard, which provides the ability to manage any data that has already been synced. It also contains an Advanced… button, which opens Chrome’s Advanced sync preferences popup.
To uncouple the local Chrome user with its server-based companion, simply click on the button labeled Disconnect your Google Account…