Stock Moto G running 4.4.2, initially set up using Motorola Migrate to transfer my data from an HTC Desire S.
I have Google, Skype, Facebook and LinkedIn accounts on my phone, and all the correct contact details from all those accounts are shown in the People app. Happy days.
The fun starts when I open the dialer, and select "All Contacts". Here I see all sorts of ancient contacts who did once exist on my previous phone(s), some of whom I may have called at some point but most of whom I never have. They don't exist in the People app, or in the Call History, or on my SIM card—indeed, if I tap one of them to look at their details, there's an "Add to My Contacts" button there.
Some of them are contacts that I used to have on my phone 1 or 2 phones ago and long since deleted, others appear to be old details for contacts that I have since updated or renamed.
Where have these ghosts come from, and how can I banish them?