Folks across the internet are upset that the nearly 800 members of Congress, state governors, and Democratic Party honchos known as superdelegates could decide the winner of the Democratic nomination. If the pledged delegate count (i.e. the delegates won through primaries and caucuses) is close going into the convention, the superdelegates' votes will be decisive, and who knows what they will do: they may vote for the candidate who got the most pledged delegates, or the candidate who got the larger share of the popular votes, or the candidate who won their state, or whomever they think is best for the country, or whomever guarantees them the most/best patronage in the next administration.
Point is, everyday folks are angry that the nomination won't be decided in a purely democratic fashion. MoveOn.org and Open Left are taking action: if you're worried about superdelegates, check them out.