First of all the value that is calculated has nothing at all to do with any actual value your blog has. The widget was developed by Dane Carlson and is based on the work of Tristan Louis's research into the numbers behind AOL's purchase of Weblogs, Inc.
Basically the original idea was that AOL paid maybe $25 million for the Weblogs company. Tristan Louis then threw away all assets of the company except for the blogs. The blogs were weighted based on Technorati ratings. Then the $25 million was divvied up among the blogs to give them a "worth".
Dane Carlson has done the same thing, upon request of a blogger asking for widget code, and divvied up the same money among all blogs in Technorati. So your blog "worth" includes the value of furniture and equipment, advertising contracts, etc that were held by Weblogs at the time of the AOL purchase.
The second thing that most people do not realize is that the widget does not calculate your "worth," but instead displays a static number embedded in the widget. So as your actual authority changes in value, the widget still displays it's initial worth.
Still, it is nifty if you like meaningless nifty things because everyone else is doing it. Here is my worth widget:
Get yours at http://www.business-opportunities.biz/projects/how-much-is-your-blog-worth/