I had a serious problem with my Mac running out of disk space. I wasn't adding anything, but I started getting warnings that my 'disk was running out of space.'
I downloaded DaisyDisk to help diagnose where the problem was. I found that in my 'Library > Application Support > AddressBook >' ONE CONTACT IMAGE keep being written in to the Sources directory.
I went into the contact nad changed the image, then the new image kept getting re-written to disk. Over and over again.
A Google search lead to to this fix, Fix: Mac is Running Slow due to AddressBookSourceSync.
I am implementing it now, and hope it solves my problem.
Posting it here in case someone has experienced the same thing.