Just discovered the following behaviour when syncing my Andorid phone with Z-push.
Name: Rembrandt van Rijn, Email: email@example.com, Phone: 071 1234567
Sync the phone. Rembrandt is now added to the phone. :)
In GO, change his email address. For example to firstname.lastname@example.org
From the phone, give Rembrandt a call. (regular phone call)
Sync the phone again: Rembrandts email adress is set back to email@example.com in GO (!)
There probably is a field in the phone for "Last call". This triggers GO sync to believe that the phone has the most recent version of the contact and syncs all fields.
If a contact is updated in GO, those changes will be destroyed and reverted (automatically and invisible) by a phone user simply calling the contact and the syncing hs phone.
Perhaps someone with an iPhone could also test this?