Hi,

I've added a wish list item for this in our project tracker. However since our site maps are dynamic and not static files they do already get updated automatically. Pinging might have some benefit to let them know it has changed but I'm pretty sure they will see those changes anyway because once you have submitted your site map via webmaster tools they will periodically check it for changes anyway. Nevertheless, every little thing that can help with SEO is worth doing so I will definitely get to this as soon as I get a chance.

Best,

Joe