The single most revolutionary thing about the Internet is that anyone can upload, and access, anything on the web, from anywhere. On one hand, this has been a boon for free speech, giving a voice to millions of people and allowing them to express themselves and share information in previously unimagined ways. On the other hand, however, it allows people to conduct illegal activity - from piracy of copyrighted material to hosting of confidential information and illegal pornography. The free nature of the Internet makes it especially difficult for governments to regulate - illegal content can be hosted in other countries with less strict laws, out of control of that government.
There is much debate as to how content on the internet should be censored, if at all. There is a fine line between enforcement of law and protection of free speech, and the two are often not mutually exclusive.