You know, this made me think for a while. This answer may not be what you asked for, but I hope help people think about this, even if a tangential way.
I checked a bunch of questions around the site. Most of the time, like here, here or here, the question seems to be about the rules, without the need to completely stick to the rules as published. Those questions are more about how to proceed in a given situation (be it RAW or by some interpretation) than really using the literal text from the books.
Questions that are "Truly RAW" are a bit different. Are humans living creatures? By the rules, that is? is an example - the querent explicitly rules out anything that is not written on the books - it's about how rules, as written, interact with other and what happens from there. My question about Night Elves and Volcanos is also a "Truly RAW" question, despite not having the tag. It is not about how to rule a given situation, is about what happens if you take the book literally. This question from KRyan is, maybe, one of the best examples of what I would consider a good use of the Rules-as-Written tag: he explicity says that he doesn't want non-published material and what he already researched, and his question is about finding a set of rules for a given situation and how them would work.
The thing with Rules-as-Written is that it is a tricky subject. You need to make clear what is ok and what is not on your question if you want useful RAW answers. RAW could be Core-only, Core-Plus-Splatbooks, Core-Plus-Splatbooks-Minus-Rules-Compendium, Core-Plus-Splatbooks-Minus-Tome-Of-Battle-Cause-My-DM-is-Crazy, Core-Plus-Splatbooks-Plus-Magazines, etc, etc, etc. And that's only for D&D. What, exactly, would be RAW for games that are massively subjective? Or for games that have a WTFazillion of modular, non-exclusive splatbooks, like GURPS?
Heck, some DM's even consider Flavor Text as rules. They are written on the book, aren't they? This whole thing of "Rules as Written" is, ironically, pretty subjective.
So, people that really want a by-the-book answer will say that out loud in the question, citing what is the valid material that could be referenced. Most of the time, however, our users are mostly interested in figuring how to use the rules in a given game.
So... What I see, from my random browsing, is that what is really happening is that people are often just asking "rules clarification" questions — a sister to RAW questions, but with lesser constraints, where new users are basically saying, "Hey, I need help understanding this set of rules!" I know that this behavior is supposed to be the SE's default, but most of newcomers are not aware of that and tag away with rules-as-written.
Moar audits!
This one seems to be wanting a house-rule, not a RAW answer. The asker explicitly says that the RAW, as it is, is not enough, and wants a solution for that. The accepted answer is, indeed, a house-rule. The questioner however commented this:
I added the rules-as-written tag to the question to indicate that I
prefer solutions which can be applied consistently with little
interpretation necessary
Which made me unsure if this is a use case for RAW or not. To me, it is a case of house rules, not RAW.
Is the product of the Heavens Mystery revelation "Coat of Many Stars" a valid target for Magic Vestment? and Does an Enhancement bonus on clothing become an Armor bonus? are, because they are by-the-book clarifications, indeed RAW.
How can I keep the Tarrasque "dead"? explicitly asks for RAW, so, it is, indeed, a RAW question.
Can the heal spell (and other positive energy effects) work on constructs? wants to find a rule to a given situation, and the querent explicitly asks for RAW, so it's ok to tag as such.
When exactly do "once each round" effects work? wants answers supported by the rules. This is different from RAW, mind you, since RAI can be argued to be "supported by the rules", too. I would tag this one with Rules Clarifications, not RAW, since RAW is about taking rules literally. This question would welcome RAI, I think.
Can you intentionally fail a skill check? uses RAW for defining the preference for a given set of rules but, in their own word, they are not mandatory. I would just remove the tag here - you don't need to tag something as RAW if it is just your preference, you can just spell it out on the question. RAW questions should be about taking the book literally.
Master of Shrouds Summon Undead caster level is explicity a Rules Clarification question, that seems tagged RAW because of the lack of a more appropriate "Rules Clarification" tag.
Does the rider need to expend an action to ride a horse? is a RAW question, and it says so out loud on the last line. It could be a rules-clarification question, easily.
Are there rules for called shots in D&D 4e? is not a RAW question. This question is asking for rules or ideas about how to deal with this, there is no apparent need for a by-the-book answer. The tag was not even part of the original question, and was added later, by another user.
I will expand the first 3 questions, to explain why I think they are not RAW.
Is a Bluff check necessary when telling the truth? - I think this is not a RAW question. Here, we are not dealing with rules interactions. We have the explicit aknowledgement that this may be the case of DM-Fiat, and this question is not about some strange, bizarre use of the Bluff Skill. To me, this is just a rule-clarification, and not a rules-as-written case.
Can I choose to grant Combat Advantage? - This one is a bit problematic. At first, I don't see any evidence that this question should be using the RAW tag, however I don't know what exactly happened on comments and, by what SevenSidedDie said on comments below, this question appears to be an exception and not representative to the question at hand.
How does shaking off hold person work? - This is just a rules clarification question. There is no aparent need for the RAW tag, and the user is indeed a new user, so he may not be aware of what exactly RAW means on the context of this community. This appears to be a rule-clarification case.
