Instead of chips implanted in the skin, why not just have a single personal card that act as ID/passport, healtyh care, credit/debit card, and could be used for any club membership too. Actually it's not so difficult technically. I already have a international debit card that can be used as telephone card, and the EU is going to impose a EU-wide health card (that some countries already have, as I do), with a chip that is only readable by special machines that each hospital, pharmacy or doctor should have. So instead of carrying loads of insurance papers, vaccination card, medical history, etc., everything is on the card. It's safer than papers as nobody can read them without the machine.
I heard that in some countries like Switzerland, they already have card-like passport, where all the visas and "stamps" are added electronically (but not all customs are equipped to read them !).
That wouldn't e too difficult to combine all of these in a single card. Then all shops and clubs should be equipped with a machine that allow them to add/edit their own memberships, without having access to other data (with password system or something).