A word of warning!
If you use the contacts database in Sitecore 8 you might run into some serious issues when upgrading to Sitecore 8.1 Update 1.
It seems that the datatype of the GeoIp has changed length from 4 to 16 characters. The 8.1 code does not handle the backward compatibility at all. :(
I started a ticket with Sitecore Helpdesk on this issue, and was asked to run this little tool on the MongoDB Analytics database.
https://dev.sitecore.net/Downloads/Sitecore_Experience_Platform/Sitecore_81/Sitecore_Experience_Platform_81_Initial_Release.aspx
That seemed to solve the problems.
Thanks to Alexander Vasilenko and Ivan Sheyenko from Sitecore Helpdesk for helping solve this issue.