BananaFish - 3:45 pm on Jan 30, 2008 (gmt 0)
The speed of light aside, DNS is mostly cached. It's not checked at the authority level (ie your name servers) every time someone accesses your site. Since the DNS is cached at the end users ISP, there is no advantage moving your DNS server to a closer geographic location to you visitors. If anything, move the web server geographically closer to your users, then they'd see a performance gain.