[Israel.pm] DNS Servers in Perl...?

[Yuval Yaari]

Offer,

I've seen these modules before but...
Is it possible to give every user a different reply?
What if the user's using his ISP's DNS server which is going to cache my 
server's reply anyway (coming to think of it, the ISP can't be global 
and will be in one country...)?
How can I make my DNS server "aware" if one server falls?
Any algos for getting the closest server by the user's IP?

Most important, why didn't anyone do it already???
Except maybe for 3DNS by F5, but that must be expensive...


  --Yuval