There is another story behind this, which demonstrated in 1517 what most might think is a modern phenomenom.
The 95 theses were written in 1517. Supposedly, Luther didn't nail them to the church door, he posted them on a bulletin board outside of the church, and sent copies to the church leaders. These comments were directed at Johann Tetzel, a Dominican friar who was selling indulgences to help fund Pope Leo X's pet project: rebuilding St Peter's Basilica in Rome. As the resident theologian, Luther's original intent appears to have been to generate a scholarly discussion amongst church elders for what he saw was the commercialization of faith.
Indulgences, in that time frame, were a written document that gave forgiveness for sins committed, or forgiveness for sins that might be committed in the future, in return for a monetary contribution. Originally, they were hand written, in a time when not many people had the ability to write and those that could were kept very busy, so they were fairly rare, likely reserved for a few wealthy people. With the written indulgence, you didn't have to beg for forgiveness, you just turned it in and were forgiven.
But, note the date - 1517. Something else had happened, about 60 years earlier - Gutenberg had created the first printing press with moveable, reusable type. As a direct result, both the time required to produce a document, and the cost of producing that document, plummeted.
One of the first heavy users of the printing press was the Catholic Church, who was employing legions of scribes to copy scripture and other church documents. And, yes, indulgences went from something that was fairly rare due to the high cost of having it written, to something that could be turned out in the hundreds of copies, for little more than the cost of the paper. By 1517, the printing presses were cranking out indulgences as quickly as the presses could operate. Now, they could be produced at such a rate as to be salable to anyone, not just a select wealthy few, and friar Tetzel was marketing them to everyone.
That's when indulgences began to get out of hand... the church slipped into using them as a money generating tool, because they were now so easy to create. This is what Luther objected to - that the church was generating profit from what should be faith.
However, the story doesn't end there, and in the remaining tale can be found the other great impact of the 95 theses.
Luther not only sent copies to the church leaders, he also gave out copies to friends. Some of those friends had access to... a printing press. And, yes, they had copies printed up. Quite a few copies, as it turned out.
This Economist article describes what happened next.
Although they were written in Latin, the “95 Theses” caused an
immediate stir, first within academic circles in Wittenberg and then
farther afield. In December 1517 printed editions of the theses, in
the form of pamphlets and broadsheets, appeared simultaneously in
Leipzig, Nuremberg and Basel, paid for by Luther's friends to whom he
had sent copies. German translations, which could be read by a wider
public than Latin-speaking academics and clergy, soon followed and
quickly spread throughout the German-speaking lands. Luther's friend
Friedrich Myconius later wrote that “hardly 14 days had passed when
these propositions were known throughout Germany and within four weeks
almost all of Christendom was familiar with them.”
Thus, Luther experienced in 1517, what we think of today as 'going viral'.. an individual's words or creations resonating with a large number of people, because they could be communicated to a lot of people.
Luther's 95 theses are not only important for what they said, they are important in showing the power of mass communications. Luther wasn't the first person to raise these issues, but he was the first one to have his thoughts communicated en masse... courtesy of the printing press. With printed copies all over Europe, he couldn't be silenced, or burned at the stake as a heretic without serious repercussions for the church. Too many people had read the theses, and agreed with them.
Thus, began the first full fledged public relations war. Seeing the power of mass communcations, Luther embraced it wholeheartedly, and invented the pamphlet, a short document written in German, not Latin, so locals could understand it, and being a single folded sheet, it could be produced in a couple of days, when publishing a printed book could take over a month.
The unintentional but rapid spread of the “95 Theses” alerted Luther
to the way in which media passed from one person to another could
quickly reach a wide audience. “They are printed and circulated far
beyond my expectation,” he wrote in March 1518 to a publisher in
Nuremberg who had published a German translation of the theses. But
writing in scholarly Latin and then translating it into German was not
the best way to address the wider public. Luther wrote that he “should
have spoken far differently and more distinctly had I known what was
going to happen.” For the publication later that month of his “Sermon
on Indulgences and Grace”, he switched to German, avoiding regional
vocabulary to ensure that his words were intelligible from the
Rhineland to Saxony. The pamphlet, an instant hit, is regarded by many
as the true starting point of the Reformation.
Luther also became a prodigious author. The church responded by holding the first organized book burnings... of his published works.
It is true that simply printing the 95 theses didn't bring about the Reformation... but Luther's words, because they resonated with so many of the general population, became a rallying point. The situation went from 'I don't really like the church' to 'let's get rid of the church and start our own'.
For another take on this most interesting story, review the 'A Matter of Fact' episode of the James Burke series The Day the Universe Changed.