Here's an interesting video link left in a comment box by PBJ:
Social media in the 16th Century: How Luther went viral
The video highlights the use of the printing press as well as the failure of the Roman church to take Luther's protest seriously, much like a big company thinking, "why worry about something on the Internet?"
Some of my favorite works on this topic are from Reformation historian Steven Ozment. Protestants, The Birth of a Revolution presents an interesting look at the spread of the Reformation. I didn't find a free Google preview of it, but Amazon has "look inside" available (as well as used copies available for around 2 bucks). This is a very readable and popular treatment of this subject.For a more detailed examination, Ozment's The Reformation in the Cities is available via Google's limited preview feature. This one is a little more expensive.