Censorship is the suppression of speech, public communication or other information which may be considered objectionable, harmful, sensitive, politically incorrect or inconvenient as determined by governments, media outlets, authorities or other such entities.

Sometimes, media censorship may be done to serve the vested interests of the governing authorities. Let's say that a foreign news channel is running an unbiased documentary on the leadership of your country, the governing bodies of your country cannot do much about what that person or channel is saying, except stop the people of your country from tuning into such shows. Hence here, censorship is used to keep the ignorant, ignorant.
I had previously made a point about how taboo topics like sex are best censored, but just because they are taboo topics, doesn't mean that they ought not to be dealt with maturely. Sex education and awareness of STDs and AIDS needs to be spread in many countries and you cannot brush these pressing topics under the carpet as taboo topics. The question is what to show and what not to show.
Is ignorance really bliss? About some things, maybe. But the knowledge about the emerging technological trends and innovations needs to be spread among the people of the world. If knowledge doesn't spread, then it leads to intellectual stagnation. The search for knowledge is what has brought humanity to where it is today, and suppression of knowledge would be a step backwards rather than forwards.
How much freedom is good? Censorship they say negates the freedom of speech. What's the point of your right to speak if there is no one to listen to what you are speaking? Then why speak at all? Doesn't the very concept of censorship clash with the idea of democracy? Then if we are going to cover the ears of our listeners, then what is the difference between democracy and dictatorship?
To conclude, the cons I would like to say that censorship is all about degree. About how much to show and how much...