The development of online privacy protections is at a critical moment as policy makers in both the U.S. and European Union push for changes to their privacy rules, but coordination of enforcement across the Atlantic Ocean may be tricky, several privacy experts said Monday.

As the Federal Trade Commission prepares to release a new framework of privacy principles to prod the Internet industry toward tighter protections for consumers' online data, one of the agency's commissioners said that she has grown particularly alarmed at the unchecked actions of data brokers to mine, analyze and potentially sell sensitive information.