In her post, Tessa makes great points about cultural truth and the philosophy of information, and as she mentions, Stephen Colbert has raised legitimate and hysterically funny concerns about the truthiness of an encyclopedia that anyone can edit (as well as introducing the term Wikiality into the public vocabulary). His position on elephants serves to remind us that just because sixty thousand people agree on something, that does not necessarily make it a fact.
So, I love Wikipedia for the little things. For example, if I want to know what year supervillain Solomon Grundy first appeared in DC Comics, Wikipedia is basically amazing (and yes, I have in fact wanted to know this and the answer is 1944).
I trust this answer, and not least because I trust that there are countless experts/fans/nerds who will modify the entry in a heartbeat if it doesn’t reflect the date on their original issue of All-American Comics #61. There’s a pretty endless supply of specialized pop culture information out there, and the people who possess this information tend to feel very strongly about it. In Wikipedia, they’ve collected what they know in searchable-database form and are maintaining it every day.
The information is the kind that’s verifiable and objective, but which the majority of people do not keep readily available in their heads, and in this capacity, I’m very much inclined to trust the hobbyists. For history, politics, botany, and medical information, I like books. But for things pertaining to pop culture media, it’s nice to know that someone is out there, keeping track of dates and film appearances and discography so that I don’t have to.