Widget code is not working on WordPress.com Hosted Blogs in WordPress

WordPress.com doest allow you to post javascript.

From WordPress.com Support:

Users aret allowed to post JavaScript on WordPress.com blogs. JavaScript can be used for malicious purposes. As an example, JavaScript has taken down sites such as MySpace.com and LiveJournal offline in the past. The security of all the blogs is a top priority and until we can guarantee scripting languages willt be harmful they willt be permitted.

JavaScript from trusted partners, such as YouTube and Google Video, is converted into a WordPress shortcode when a post is saved.