linked accounts result in random behavior regarding which account one logs into
I loged into facebook and suddenly saw completely different cardSets.
In the database I tracked down these cardsets and it turned out they were from my G+ account that I had linked to my facebook, too.
removing facebook from the linked accounts allowed me to log in to my primary (fb-based) account again.
(This was a shocker! All my cards – gone!)
resolution would be to merge accounts if somebody tries to link an account that already is linked.
Issue is closed for Release alpha 0.