"The bookmarklet is clever, but still I think it's too inconvenient to become very popular," comments Ryan Morehart. The worst thing is that you need to click on the bookmarklet whenever you visit a new page and every time you click on the bookmarklet, it opens a new pop-up window.
Google Sidewiki's team says that it works on a Chrome extension that will add more features and it will be better integrated with the browser.
{ Updated to correct an error. Thanks, Peter. }