On the subject of DNS GSLB, there's a fairly well known article on the subject that anyone considering implementing it should read at least once.... :)
http://www.tenereillo.com/GSLBPageOfShame.htm and part 2 http://www.tenereillo.com/GSLBPageOfShameII.htm Yes it was written in 2004. But all the "food for thought" that it provides is still very much applicable today.
