The company added that the tool wasn't in response to a specific incident. However, the firm does expect to reexamine its involvement with outside data measurement partners to ensure they handle info in a responsible way.

Whether or not this is a reaction to Cambridge Analytica, there's no question that Facebook has been improving its privacy controls in the days since the data sharing scandal became public. In addition to slapping restrictions on third-party data providers, it recently introduced a simpler way to manage and delete data on your phone. Facebook wants you to know what you're sharing and where that data is going.

The main question here is implementation: how will this permission tool work? Facebook declined to elaborate, so it's difficult to say whether the tool will actively enforce the email requirements or just obtain promises. If it's the latter, that could be a problem. Facebook's terms didn't prevent the misleading data collection and sharing in the Cambridge Analytica mess -- a stern warning isn't likely to deter unscrupulous advertisers bent on collecting your email info without asking.