Rules of the House

I want to begin this post with a brief anecdote. 
The other day, a friend of mine with whom I've gamed for many years, confessed to something he considered "embarrassing." What was the source of his shame? He recently tallied up the pages in the house rules document for a game he was refereeing and discovered, to his surprise, that it exceeded sixty pages. The horror! I was quick to reassure him that this was no cause for unease. Indeed, quite the opposite, since these rules were, in part, the accumulation of years of thought and play – tweaks to make the game "as [he] would like it to be," in the phrase from the afterword to OD&D. 
My friend's reluctance to admit that he very thoroughly house ruled the game he was refereeing is not unique. Over the years, I've encountered quite a few people who have felt that the addition of house rules was somehow "wrong" and that the only "correct" way to play a RPG was exactly as its rules were written. I'm not quite sure of the origin of this mentality. If I had to guess, I'd lay the blame on the third edition of Dungeons & Dragons, part of whose culture is obsessed with "RAW" – "rules as written" – a term that I don't believe I ever heard prior to 3e. I don't want to lay the blame entirely on this edition; Gygax complained about rules lawyers all the way back in 1974, so the mentality has been a constant in the hobby, even if its prevalence seems to have increased in recent years.
I don't think I've ever played a single roleplaying game exactly as it was written. In some cases, this was due to ignorance or misreading of the rules. In other cases, it's because of the existence of a body of folklore that has supplanted the actual rules to the point that "everybody knows" this rule or that should be understood in a particular way (often contrary to the designer's intent). Yet, there are also examples of rules changes that are deliberate and the result of careful thought and consideration, added or subtracted to make the game run more like what the referee and players desire. 
Like rules lawyers, this is a venerable tradition, predating the existence of OD&D itself and arising out of the traditions of miniatures wargaming. Arguably, the entire history of RPGs is, to borrow from Benjamin Jowett, a series of house rules to D&D, sometimes explicitly so. Neither Gary Gygax nor Dave Arneson played OD&D precisely as written. From a certain perspective, AD&D might even be called an elaborate set of OD&D house rules, with the game expanded and honed into something Gary found more congenial to the style of play he preferred. There's nothing wrong with house rules and I must confess to be baffled that anyone might seriously think there were.
That said, I do feel that, before one introduces house rules into one's campaign, it's important that one reads, understands, and tries to use the rules as they are written. "Ivory tower" house ruling, which is to say, pre-emptive house ruling before play has actual begun no longer sits well with me, even though (or perhaps because I have engaged in it in the past). I am now much more firmly of the opinion that house rules should arise from play and reflect dissatisfaction with how the actual rules work in a given campaign. In this context, I find house rules not merely laudable but in fact inevitable. Any referee running a long campaign will, I think, introduce house rules into play simply because no RPG ever written is so perfectly written that its rules work for every possible configuration of players.
Again, I'd like to stress that I generally don't think house rules should occur in a vacuum. They should be reflective of play, not to mention reflective of thoughtful engagement with the rules they're supposed to modify or replace. Taking the time to read and understand the rules of the game you're playing seems to me to be a prerequisite to the creation of any house rule. Perhaps I am odd but that strikes me as commonsensical, after the fashion of G.K. Chesterton's metaphor of the fence: "don't tear it down until you know why it was put up in the first place." I think that's sound advice and have tried to put into practice in my own campaigns.
There is no shame in house rules, because they are almost unavoidable if you play a game long enough. That's exactly as it should be, which is why OD&D ends with an exhortation to make the game as you would like it to be. Fight on!