Lurking is an activity performed on Internet Forums that involves wandering the website, reading posts and never actually posting anything. Most internet forums do not charge for access to post, so in many cases "lurkers", as they are called, are completely anonymous. However, in special cases, such as on the Something Awful Forums, lurking is necessary with an account because not all forums are visible to the general public.
Most forums encourage lurking because it gives the user a better feel for how the forum operates and what kind of people its userbase is made up of. In most cases, a combination of reading the forum's FAQ or rules and lurking will guarantee that the user in question will never be banned.
Wikiwhatever.