Lewis Pulsipher @ Gamasutra: "I'm always amused when my game design students complain that someone is "camping" in a shooter game. (They play at the game club, not during class!) They're trying to enforce some kind of standard of "honorable" behavior through peer-pressure, it seems.
Yet I always tell them, if the game allows a player to do something that is a good strategy, some players are going to do it--I would. (In the same sense, "turtling" in a boardgame might be frowned upon, but if it's the best strategy for a player, some are going to do it.)
In other words, if the game fails to make camping (or turtling) an impractical strategy, yet the result is undesirable, there's a defect in the design."