When you click a Like button on Facebook’s site or one of the zillions of other sites that Facebook has aided/infested, are you speaking? One could argue no, you’re just clicking a button, you’re not actually saying anything. One could also argue, yes, you are taking a shortcut but you are indicating that you like something, that you approve, you are saying “like”.
A judge in Virginia has ruled that four employees of a local sheriff who Liked the page of the sheriff’s opponent in an upcoming election were not fired unfairly.
From the LA Times:

In citing other cases of protected speech on Facebook in his decision, the judge notes that, unlike the simple act of clicking “like,” actual statements were made.

The Times quotes a dissenting opinion from the ACLU:

“The key question is, is the act of ‘liking’ something of Facebook, does that express an opinion or thought,” said Aden Fine, senior staff attorney for the American Civil Liberties Union in an interview with The Times. “It certainly does. The mere fact that you’re pressing a button to express that view or opinion instead of saying those words doesn’t make a difference.”