The reason why social media has much more impact than the printing press had, or the telegraph had is just two simple things: price and access. The introduction of the printing press was great, especially when everybody was allowed to print the things he or she wanted. However not everybody had a printing press at home, or event in their street or city. Printing presses were scarce and they were expensive and they required specific knowledge to work with. So allowing everybody to print everything they want was something easy.
A revolution with a handicap
Same goes for the telegraph, when it was introduced, people could get more connected, whenever you were close to a telegraph. Though still it was rather a one-to-one medium just like the printing press (or in best case: one-to-few in case you were printing posters or made sure the message via telegraph was read out loud in a group). However social media has not these limitations, first of all: for most people it is not expensive to do anything with social media nor is it hard to understand how social media tools work (700 million people figured out themselves how Facebook works).
It is not as revolutionary
Therefore Social Media is not as revolutionary as the printing press or the telegraph, it is more revolutionary. More people can use, more people publicize and more people can be reached via social media. By its open nature every message is often public on social media, making it potentially reach everybody who has an internet connection and some kind of browser.
The printing press was limited from the start, therefore everybody was allowed to publish the things they want, just for the simple reason there were so many constraints that it hardly would happen. Now with social media everybody, independent from your wealth, race, background, network or anything else, can reach everybody. The only thing you need is an internet connection and a message that is worth to be amplified across social media.
It is better than the printing press
Social Media is more revolutionary as the printing press, it is the printing press as it was intended: free, easy and with the potential to change the world by getting your message out to others.