According to Wikipedia, "In the context of fiction, the canon of a fictional universe comprises those novels, stories, films, etc. that are considered to be genuine, and those events, characters, settings, etc. that are considered to have inarguable existence within the fictional universe. In order for the fictional universe to appear cohesive, especially in fictions that contain multiple parts, both creators and audiences sometimes find it useful to define what has and has not "actually happened" in that universe. Usually items that are considered canon come from the original source of the fictional universe while non-canon material comes from adaptations, spin-offs or unofficial items, often in different media."
The term has been very popular with LG users speculating on whether or not charcters on YouTube are an official part of the LG universe or not.
The following list is highly speculative and the relative probabilities will probably change over time. This list just represents an "educated guess' by the user community based on the current available information. To provide a standard "litmus test" a character will not be declared official until they are included on the video list of lonelygirl.com. At that time they will be removed from this speculative list.