Over at the Chicago Faculty Blog, Saul Levmore asks an interesting question:

  Why do we see fines for littering but but not for cellphones ringing in the middle of movies and concerts? I'm afraid the question is better than any answer I have to offer. . . . [Consider a] fellow who "negligently" lets a paper bag and its contents fly out the window of his car. In that setting, we resort to fines rather than torts, though that must be in part because the littering is on public property. The cellphone wrong is often on private property, and littering is normally a misdemeanor on public property.
  [On the other hand, consider] smoking, where smoking is banned. . . . [F]ines for smoking are common both in public places and in private places subject to public regulation. Someone who smokes in a banned area, including a restaurant, in Chicago is subject to a $100 fine; the non-complying owner also faces a $100 fine for the first offense, and then $500 for a second offense.
  The problem is of course a trivial one as problems go. But it points, first, to the interesting set of behaviors that constitute negligence with no enforcement through tort law and, second, to the problems that generate political pressure for fines (publicly or privately stipulated), even though fines are less calibrated (to the level of injury) than are negligence suits.

  Having enjoyed going to the movies with Saul before (no ringing cellphones that I recall), I thought I would venture a guess. I think the main reason boils down to mens rea. Mens rea is Latin for "guilty mind," and is usually used in criminal law to mean the person's state of mind with respect to the underlying offense. It's a critical concept in criminal law, if not the critical concept, because an actor's state of mind with respect to a harm generally reflects his culpability. The basic idea is that intentional acts are most likely to justify punishment while negligent acts are much less likely to justify punishment.

  I suspect mens rea explains the different treatment here. Littering and public smoking are usually intentional acts. "I really need a cig," the smoker might say to himself. "Someone else can clean up," thinks the litterer. There may be exceptions, like someone who doesn't realize he is littering. But I suspect the exceptions are relative rare, and I would guess enforcement in that setting is low. On the whole, the conduct is intentional.

  On the other hand, a ringing cellphone is usually if not always an accident. I've never heard of someone intentionally ringing his cellphone in a movie or concert. The conduct we want to deter is the failure to exercise due care in making sure that your phone is off or set to vibrate just in case someone else decides to call you. The possible wrong is garden variety negligence, not some sort of intentional act, and is therefore considerably less culpable. So we let social norms take care of it, aided by the now-ubiquitous pre-show reminder to turn off cell phones that emphasize the norm and encourage people to follow it.

  UPDATE: As noted in the comment threads, it seems that New York City has such a ban, with a $50 fine.