Most people respond that freedom of speech is the right to say whatever you want or to voice your own opinion. While this makes all of you feel better knowing you wont be murdered by your government for speaking your mind, this is just a minor point in its relevancy to society. Few people realize that actions are really what enables society to progress through freedom of speech. MLK's I have a dream speech was not nearly as important as the simple act of a black man, in those times, walking up to the podium to speak for the oppressed. Freedom of speech is changing your online habits to avoid NSA spying. Freedom of speech is all of the small choices you make daily that you don't even think about.
In the age of the internet people still fail to realize that real life and internet, while connected, are not one and the same. On the internet you are given the choice to choose how you represent yourself. In real life you are represented by the way you look, by the color of your skin, by the clothes you wear, by your accent, by your gender and many other arbitrary things. On the internet none of these things matter. Considering this imagine an account on twitter had images of swastikas and they said the word "nigger." Most people pass by that account assuming they are inherently racist. The internet is made up of free speech and symbolism displayed on a screen. Its not made up of anything tangible. Its 2013 and people are still offended by words and symbols on a screen. 4chan has used words and symbolism not to define itself but to keep out the people that have failed to understand them in real life. People that don't get there jokes and fail to grasp the simple ideas spread around. Maybe the twitter account posting swastikas just wanted to offend you and keep you out of their mentions.
Even the "negatives" of free speech are relevant to society. Freedom of speech doesn't mean you get to choose who gets to use it.
Recent revelations about NSA spying have back the terrible phrase, "If you have nothing to hide, you have nothing to fear." this is a statement that gets put out without any real rebuttal to why or how it is so detrimental to the growth of society. We know that people willing give up liberty for security in our "Free" society. I feel they would be less inclined to if they knew the harm it caused. Spying is censorship. If you believe that everything you type up on a digital device, or the words you say on a cell phone are be listened to you will begin to censor yourself. You start becoming afraid that the people spying may not understand what it is you are trying to say and think you have malicious intent. We have seen this happen too many times. We have the facebook rapper, the tumblr experiment, the airport sandwich guy and so on. Spying forces people to revoke their own freedom of expression.