The banks argue that consumers may unknowingly be putting their data at risk because they keep so much of the confidential information in a single place, said people familiar with their position. In addition, it isn’t clear if consumers’ finances would be protected if they willingly handed over their confidential information to a site that was later hacked, they said.

That issue hasn’t been tested because no aggregator has been the victim of a known major data breach.

Source: Big Banks Lock Horns With Personal-Finance Web Portals – WSJ