Censorship is nothing unique to old fashioned dictatorships. There are lots of things that you are not allowed to say in todays western democracies.
In many countries you are not allowed to deny certain historic events and certain war crimes in public. Some countries have laws against blasphemy. In some you can not make statements that may be perceived as supportive for certain ideologies or militant organisations. In a few countries you may not be overly positive about homosexuality in public. In others you may not be offensive on HBTQ matters. And most countries have laws against hate speech — that are especially troublesome, as they give certain groups and individuals special rights.
Until recently, the red line was drawn where you made a public speech, published a newspaper article or distributed a leaflet or a poster. But today it has become more complicated.
Should a tweet be considered a public statement? A Facebook post? An Instagram picture? An e-mail on a mailing list? A G+ post to your personal circle of friends?
To complicate things further, the Internet knows no boarders. What is legally published in one country can be read — and illegal — in another.
With mass surveillance you must assume that the government is picking up on everything you do on your computer, smartphone or tablet. If the government wants to know what you are up to, it will know. This might lead to operations like in France recently, where the authorities have been trawling social media for people who might have defended terrorism in one way or another.
There are even cases in Britain where personal SMS/text messages have been enough for the police to knock on the door, asking people what they are up to.
Censorship and mass surveillance is a particularly bad combination. It will create a mental Panopticon.