So the solution to that is publishing all your transactions to a public ledger?
(yes I know there are "tumblers" etc, but these come with operational and practical issues)
The bank isn't authorised to provide that information to third parties.
http://www.cardlytics.com/technology/
Despite the "firewall" between the bank and the marketers, information is being sold - it just requires an extra step on the part of the marketers (leaving the banks legally in the clear).
The rest are just ideological and/or about facilitating illegal activity and irrelevant to most people. This is the problem with Bitcoin and other digital currencies. There is just not enough focus on making something better and simpler than the existing system.
You mean mainstream disadvantage.
I think most people using VISA are happy that they won't lose all their assets to fraud or theft of their credit card. Mainstream retailers accept a certain amount of fraud as a cost of doing business, only disruptive or greymarket vendors face significant risk from chargebacks.
Removing chargebacks is a positive benefit to a tiny fraction of the participants in legitimate financial services.
(1) Because not all masters are benevolent
(2) Because it removes the possibility of charge backs
(3) Because not everyone enjoys being monitored by companies and/or governments (foreign or otherwise)
(4) Underground markets are only "underground" because of laws. If a society outlaws birth control and abortions, but a women wants an abortion she probably wants an alternative (I.e. something an underground market with provide). An anonymous crypocurrancy (or cash) is the easiest way to do this. If it's not a crypocurrancy or cash, they can always trade goods. So in all honesty, there's no way to stop it.
There may even be other reasons, but it seems pretty obvious it can inherently good to have.