Companies like Unroll.me have long acted as intelligence services offering insights to businesses seeking to gain a competitive edge. Both Uber and Lyft pay for information from Slice as well as other data services, according to two people familiar with the companies’ competitive intelligence programs, who asked to remain anonymous because the programs were confidential. Uber and Lyft declined to comment.

Unroll.me, which was bought by Slice in 2014, is a tiny player in the personal data market. The larger data brokers — with names like Acxiom, CoreLogic, Datalogix and ID Analytics — have been the subject of inquiries by a congressional committee and the Federal Trade Commission.

In 2014, after concluding its investigation, the F.T.C. called on Congress to protect consumers against the unchecked collection and marketing of their digital data. The F.T.C. report detailed how some of the companies classify consumers in data-driven social and demographic groups for marketing purposes with labels like “financially challenged,” “diabetes interest” and “smoker in the household.” The concern is that such classifications could be used to limit fair access to financial services or health insurance.

The F.T.C. recommendation, which was endorsed in a separate report by the Obama administration, was not taken up in Congress.

Unroll.me bills itself as offering an easy way to “clean up your inbox.” After someone grants the service access to his or her email account, Unroll.me serves up a list of all the subscriptions they are a part of, with the option to quickly opt out of the ones they no longer want to receive. The company also organizes subscription emails and delivers a newsletter-style digest of some subscriptions.

The service, which began as a test in 2011, quickly took off with users, attracting the attention of Rakuten, the Japanese e-commerce giant that now owns Slice. Rakuten invested in Unroll.me before Slice ultimately bought it.

Unroll.me discloses its freewheeling use of personal data in its privacy policy, which says that “we may collect, use, transfer, sell and disclose nonpersonal information for any purpose” and that the data can be used “to build anonymous market research products and services.”