Even if there was an option, Urchin / Google Analytics is currently only setup to allow one instance of their code on a website. Placing two voids both of them and no result are generated. That's a policy with Urchin and Google.
Javascripts are removed from all user input due to security concerns here at WP.com. If they were allowed, it would be easy to lift login cookies, offer access to the servers, and the like.
Javascripts are allowed though with the standard WordPress software available at wordpress.org that you would have to find your own host for. They'll allowed there since it would be your own site and you can do what you please with it. If you were to endanger your site here at wp.com, you would be endangering every body else's site as well.
TT is pointing that out to you since the question about adding in javascripts gets asked 10 to 20 times a week here and is already covered in the FAQ blog as well as the FAQ sticky at the head of the forums. Those resources are made avaailable to folks so they don't have to ask when the answer is already available.
We do answer the "stupid questions" here but they get answered along with a pointer to where folks need to look first before asking those questions. I just spent five minutes answering your question when I could have been answering someone's else concern that isn't covered already.
Hope this helps,
-drmike