The answer is: Twitter. Similarities are...

- Social media platform (you are the content).

- Advertisers pay for eyeballs.

- Hashtags and groups collect similar users.

- Privacy settings control who sees your content.

- Text, pictures, videos, & polls.

- People leave Facebook for Twitter, & vice versa.

I'm not sure why he didn't just say "Twitter". In some very abstract way, Facebook overlaps with Apple. But that wasn't the question. The spirit of Lindsey Graham's question was to determine if consumers have a choice, and the answer is yes, they do: Twitter.