In reality, I don't think they even need to DF you officially. As long as someone is willing to start a rumour about you to the effect that "a friend of a friend of a friend" heard that you were now Apostate?, it's just as good as DFing you ultimately. Once the rumour is out there, any JW that has heard it will avoid you like the plague.
And when this happens, you can have fun with them at WalMart. Run up to them and yell "BOO!"
Seriously, I have one cousin (that I didn't much care for when I was still a JW) in the org, still. Saw him and his wife in WalMart and they nearly knocked over an old lady to avoid me. Win/Win situation in some circumstances... this being one of them.
CountryGuy