[hassanhassan]

The future is already here. Cardlytics (a card-linked marketing company) has partnerships with 400+ financial institutions, and claims to have insight into consumer purchase behavior for ~70% of U.S. households and ~30% of U.K. households according to their Crunchbase profile.

[rahimnathwani]

As far as I can tell from their web site, the customer data doesn't leave the financial institution, and the ads appear only on communication from that institution (e.g. on the credit card statement).