Weird issue with Screen Sharing.

[octatonic]

I sold a G4 Powerbook to a friend about 2 years ago.
I just looked in my 'Shared' drop down in the Finder sidbar and I can see the laptop there.

Not sure why this suddenly happened.
Is there anyway I can get rid of it?
I'd rather not have to contact the person I sold the powerbook to- we're not so friendly these days.

Any idea why this might have happened and how it can be fixed?
I can network to it and even take control of the screen.

 

[octatonic]

Seems to be happening via 'Back To My Mac' as if I uncheck 'Back To My Mac' in Finder Prefs then it disappears (as does my Mac Pro).

Ideally I'd like to delete the old powerbook, but still be able to use Back To My Mac.

I wonder if this is something to do with them changing things at Mobile Me?