[Shooti]

> Even if the contact sync was in place, it would be unlikely that the other party would have used my 5 year old YouTube avatar and populated it with both my email and phone number and full name.If my contact on his google side was populated from my gmail; as I have emailed the other party before, it shouldn't contain my phone number either - unless google matched it and shared.

I'll repeat my alternate explanation more concretely: the name and the Youtube pic was auto-synced via @GMail, and your friend just manually added your phone number to it. It's now permanently in his Gmail account as part of Google Contacts, independent of anything done on Google's part.

Get your friend to delete his contact of you from the address book ("People") and see if it occurs again.