$ dig +short TXT google-public-dns-a.google.com "http://xkcd.com/1361/"
Turns out there are clever ways of (mis)using DNS features to make money. For example, your server could hijack NXDOMAIN responses and instead direct the user to a nice page that tells them that the name couldn't be resolved alongside a couple relevant advertisements.
This may actually be true, as google believe's that if you arrive faster to a website after searching on Google you will use Google more
Also, at the scale Google operates, I am not sure that DNS is that big of a resource commitment, and it may allow them to do fancy traffic routing stuff for their own services.
Heck, I even have it aliased as "pg" on all my systems.
It is also a DNS server.
dig +short TXT google-public-dns-a.google.com
by the way, the "http://xkcd..." part is the response, but since @asdafa didn't put \n\n after the command, it's appearing at the same line.