Question About GUID

Can anyone tell me why when I have WP installed in it’s own directory and then change the blog address to point to my domain name (in settings) the GUID addresses in the database don’t change? Everything seems to work fine but it seems to me they should change (for instance) from http://www.domainname.com/blog/?p=1 to http://www.domainname.com/?p=1. Just trying to figure out if I’m gonna end up with trouble down the road because of this. Thanks.