If you login to your verified web sites at Google Webmaster Tools and go to the "labs" section, you may notice a new feature to help you control your Sidewiki messages.
Here is a picture:
The feature basically let's you control the message you show to users who use that Google Sidewiki within the Google Toolbar. In the past, webmasters had to use the Google Toolbar to add a site owner message. Danny has a great article on how that worked at Search Engine Land.
Now this can be done directly in Google Webmaster Tools. I do not believe Google announced this feature yet.
Forum discussion at WebmasterWorld& DigitalPoint Forums.
