I accidentially moved a contact folder from one of my IMAP accounts to the other. I noticed the mistake and moved it back. Result: the folder now shows up on both accounts, the contents are gone (verified on the IMAP server). System is KDE SC 4.8.4. Reproducible: Didn't try
During Akademy we fixed it. Need to retest it will akonadi master + kdepim 4.9 branch
Reopen if it doesn't work with 4.9.2