First of all, I would like to say thank you for the great effort on making this great Q&A system. it's really great!
The auto sitemap feature is really great, and I have a small suggestion to make it even better.
On google's help page there is a small tutorial, describing a way to ping to google on changes in sitemap. The tutorial is here:
http://www.google.com/support/webmasters/bin/answer.py?answer=183669
My suggestion is to implement a feature which will auto ping google when a new question is added to the website. The ping can be done using a simple HTTP request, to the sitemap url as a parameter to google webmasters - for example, to
www.google.com/webmasters/tools/ping?sitemap=
http://www.example.com/sitemap.gz
This will be great for webmasters which are using sitemaps, and do not want to manually re-submit the sitemap to google every day or so.
Will be glad to hear your thoughts,
Thanks.