Although it's a bit late for Christmas cards this year, it seems that the Digital Landing Web site is causing a stir in some circles as it allegedly allows reverse lookup of any (or so it seems) residential phone number in the US - even those that are ex-directory (or unlisted in US phone parlance).
If you head on over to http://digitallanding.com// and enter the relevant phone number in the box in the top right-hand corner, click on compare offers now.,' the system will return the required address.
Even with unlisted home numbers.
I'm not sure whether the site operators ever intended this marketing aid to be used in this way, but until it gets zapped, I'll leave everyone to have some fun.
Happy New Year everyone...