Saw The Social Network this weekend and loved it. Totally recommend it. Not sure if it is one that you absolutely must see in theaters but it does complete the experience. The film explores a lot of how this generation socializes and how far we have come just in the last few years. The script is incredibly tight and clever, the cinematography is great (directed by David Fincher of Fight Club, Seven and most recently The Curious Case of Benjamin Button), and the pace is incredibly fast (perfect for kids of the ADD generation).
Recently saw the trailer for Catfish. The Rolling Stone claimed that it is a documentary although I am pretty sceptical.
This segment from the Disney Channel is amazingly stupid and absolutely worth watching.