I must agree with Fusangite. And I will add:
-Many people use 'D&D' to mean 'the Dungeons and Dragons roleplaying game, published by Wizards of the Coast, in its current incarnation'. And others use it as a shorthand for 'D&D and other tabletop FRPGs, as well as any crap house-ruled-to-death abomination played by people who have, at some point, read the PHB'. I assume the original post referred to the former.
- In order for D&D to achieve the same measure of mainstream respect shared by other games such as cribbage or rugby, there must be certain, intrinsic rules, sine qua non. Almost every high school in this country has a football team, and any of those teams could play any other on any high school football field because of this uniformity of rule. Further, any player on any of those teams could transfer to another team and still be sure he knew what rules he would be playing under. And if I were to say 'I ran fifty yards to the goal line,' you know exactly what I have accomplished and can measure that accomplishment against others, and no one can whisper "Yeah, but over at William Blount, they define a 'yard' as one foot, and ..." etc. etc.
Without standard rules, my lords and ladies, we may be playing at D&D, but we are not playing D&D.