US lawmakers propose bill to curb Google and Facebook's ad dominance.

A bipartisan group of US senators has introduced a bill aimed at cutting Google and Facebook's clout in online advertising, which would prohibit big digital advertising companies, with Google the biggest, from owning more than one part of the stack of services that connect advertisers with companies with space for advertisements. The bill would only impact companies that do more than $20 billion in digital ad transactions. The bill's chief sponsors include antitrust experts including Senators Mike Lee, a Republican, and Amy Klobuchar, a Democrat.