in-addr survey?

I'm attempting to convince "the powers that be" that attempting to use
reverse lookups to determine geographic locale is extremely
inaccurate. One of the reasons among the many this is the case (I
believe) is that significant portion of admins do not have properly configured
in-addr. Has anyone done this sort of survey(Bill Manning?) If so,
anyone have a pointer handy?

Thanks.

I'd have to say that the people you'll be blocking doing this will be
legitemately blocked. Now the problem comes from the ppl who don't have
reverse DNS setup properly. Lets say you'd like to block download of a
crypto software to everybody in Yugoslavia, by not allowing downloads from
everybody comming from .yu, your legimately blocking a bunch of people,
but then, everybody comming from a .com in yugoslavia are going straight
through. And you still don't have control over someone that'll decide to
dial-up all the way to another country to download your crypto software.