Creative Destructive Paradox
Just what is the difference between graffiti and public art?
  Keep in mind that no scientific or legalistic evidence has been allowed to interfere with the creation of these images or my opinionated observations.
  For starters, graffiti is often created at night by a person or persons representing only themselves and sharing deep and powerful feelings generally censored or ignored in the mainstream.
  Clearly, this highly individualized form of self-expression is also a type of vandalism and/or activism.  To a property or business owner, the difference between graffiti and public art is monumental, and usually measured in dollars and cents.
  As an outreach tool, graffiti can be used to support (or oppose) a sports team, a school, a political idea or a specific candidate.  Or it can be a highly personal combination of all these at once; an uncompromising glob of expressive visual goo.
  In the political arena, particularly during an election cycle, graffiti is a deliberate weapon often kept locked and loaded—there’s no telling how much is sanctioned by campaign managers and how much comes from passionate supporters or opponents.
  In the promotional arena, film and music distributors have mastered the art of legal and illegal “plastering” of posters all over construction areas and downtown locations prior to release day. This is considered to provide “good value” even when fines are levied and legal fees added.
  Other high-profile businesses also use similar marketing efforts, and their message can also be seen (legally) on buses and other modes of public transportation. 
Since I would not refer to a careful rendering of a business name or logo as graffiti, I would not use the term to describe anything openly funded with corporate or public money.
Graffiti art has a short life span, with little compromise involved, perhaps making it the last pure art-form left to explore in an overly commercialized culture. 
  Murals, on the other hand, are more likely to have been created during business hours (though some muralists prefer to work at night) by devoted local artists, often graffiti artists on the side. The themes, ideas and styles used may have been carefully reviewed and approved by a group of non-artists representing the funding source.
  Many original ideas suffer a quick, senseless death as they navigate the halls of the uncreative-in-charge. Still, many good murals are made this way, which is what keeps the idea of public murals alive and well in San Francisco and other cities. 
  There are also the traditional muralists, a rare and heroic breed, some of which began their careers on the street and found a way to legitimize their passion.
  Graffiti is discovered, often found on the street like an abandoned pet.
  Public Art is expected, mentioned in the local news and celebrated with openings and Sunday Magazine spreads. It is generally celebrated, loved and photographed by those that see it more often.
  Graffiti artists risk a serious confrontation with “the law,” which is not usually on their side.  If a graffiti artist with an existing police record gets caught “in the act,” it’s likely that the charge will be elevated from misdemeanor to felony (the three-strikes-you’re-out kind, which improves the scorecards for ambitious legal types not prosecuting enough “real” criminals).
  Public Art, celebrated by the same system that prosecutes graffiti artists, is often based on local ruling class conventions and assumptions. Graffiti stands as a direct challenge to those conventions.
  If Public Art tells us that we can be proud of our culture, then graffiti tells us  there are things our culture is afraid to look at, but should.
  If Public Art is a little bit country; then graffiti is a little bit rock and roll.
  Public Art takes time to construct properly, graffiti blossoms overnight.
  Public Art requires clout and skill and passion, graffiti demands passion, skill is a bonus.
  Public Art requires business survival skills, graffiti demands street survival skills.
When graffiti and public art overlap harmoniously, it is usually perceived as public art. When the harmonies are off and the orchestra out of sync, the results are often seen as vandalism.
  Public Art (sometimes also referred to as corporate art) can seem to present ideas the corporate world wishes to convey. Graffiti (when referred to as vandalism) challenges the very ideas often pushed by the corporate world.
  Public Art is a gentle love tap. Graffiti is a 2-minute warning of life out of balance.
 Public Art often (not always) shines like a new hairdo. Graffiti often (not always) sticks out like a black eye.
  Art to some, vandalism to others. In the long run, both graffiti and public art serve a unique purpose that our culture needs now more than ever.
  If Graffiti is truth, Public Art is fantasy.
  If Graffiti tells it like it is, Public Art tells it like it ought to be.
  If Public Art were a politician, it might be John F. Kennedy or Barack Obama.
  If Graffiti were a politician it might be Fidel Castro or Che Guevara.