I have the same question. I’d like to add a bit to the standard template then have that template be the default template for people who create a blog. So, they will be able to make posts but not change the template.
Of the many possible reasons this could have happened, in this case, I had not given GoDaddy enough time to set up my dedicated IP address, so the IP address they gave me for the site in my domain manager was still the ip address from the shared hosting account my site was on before I installed wpmu.