You exported a complete Contacts database. Importing replaces your existing database with the one you exported. Since your contacts were all on iCloud, and you no longer sync with iCloud, the databse is empty.
Currently Being ModeratedMar 28, 2013 6:11 PM (in response to Linc Davis)
This is real shortcoming with the Contacts application. Apple should spend more time and resources ensuring their core applications function correctly. Here's the convoluted solution from Apple support regarding this problem, I found in another thread:HT2486 Re: Imported contacts disappear after about 5 seconds
Same problem. Importing contacts lets them flash into the contacts app, and then they disappear within a few seconds to match the empty icloud website. btw. I'm in Mountain Lion on one of my macs, where Address Book is now Contacts
Spent 2 hours with apple support today with senior support person, and the following procedure fixed it for me
1. disconnect from internet (switch off wifi, or unplug ethernet cable)
2. in Contacts application, import all contacts
3. in System Preferences/icloud untick contacts
4. when prompted to delete or keep, choose keep (moves contacts to "on my mac")
confirm that the contacts are now on your mac
5. in System Preferences/icloud tick contacts
6. when prompted to replace or merge, choose merge
7. connect to internet
8. in Contacts application, drag all contacts from "on my mac" to "icloud"
9. in Contacts application, drag all groups (one by one) into "icloud"
confirm that all your contacts have been moved over and the groups are all ok
10. delete all the contacts in "on my mac"
11. in Contacts/preferences select default addressbook = "icloud"
12. sigh with relief
Come on, Apple, you have to do better than this.