I note that most comments relate to the specific question that was asked, and not to the more general question of how you go about deciding on a rules question. Noumenon has suggested asking on enworld.org, but you can’t stop play and wait a week or two or more for an answer if things come up at the gaming table. That’s why I value the Rules Compendium so highly (because it clarifies so many specific questions people had asked) and why THAT was the subject of the answers. Not criticising the people who have made comments here, just observing that very few have talked about their decision-making processes.

Note that the hill giant has a high enough BAB that it should be able to throw two rocks a turn even without Rapid Shot. I believe the issue is that it lacks Quick Draw.

also, such stones (if they could be transported) could be sold to others to figure out the “technology” for other races to use but then the question becomes how does one go about carrying such a large stone without it exploding (think of it something like a land mine or other unstable explosive(s) of today) What about a site that had partially done such device(s) in a geologically unstable area. A whole adventure could be set around finding and either safely detonating them or warning travelers that any sudden noise could set them off and cause an avalanche/ rockslide. Maybe the area could be littered with them in such a fashion to cause the entire roadway to giveway in a domino-type of fashion to destabilize the merchants in the area.

Also, primitive giants could have made an alliance with some magically advanced forces, maybe even a single powerful wizard with interests in the area, and are now upsetting the balance of power with their new found advantages.

Just my 2 cp

Second, even though I was at pains to explain every step of my thinking and research in the post, (which took quite a while), actually doing that research and reaching the decision took about 2 minutes, much of it finding the relevant pages in the rules – and would take less if I had the sourcebooks at hand (as I would if running the game at the time). So I would follow the same steps, at least on this particular question.

(My stronger talents as a GM include being able to read quickly and make a decision quickly, which helps. There was the time a purple worm tried to swallow a PC (as they do) and the PC cast a blade barrier straight down it’s throat; I had to rule on how much damage it took. It took all of 15 seconds to glance at the spell description, picture the situation in my mind, and make a ruling based on that picture; I ruled that the worm was killed instantly.

If the question was a more complicated one, or one that had greater implications for the campaign, then I would issue a temporary ruling on the spot but revisit it between sessions – and make sure that the players knew that my in-game ruling wasn’t final. It’s hapenned from time to time, though I don’t actually recollect any of the questions just now.

Finally, I like to think about the game physics perspective, even if it is wildly exaggerated, as it provides clues as to how to describe the action to the players. It’s a little splash of colour that helps the campaign seem a little more tangible even when we’re hip-deep in game mechanics.

What would you do differently if asked that same question during an encounter?

I’d personally rule that throwing a rock = using a ranged weapon, which makes it valid for the feat. Bows and slings and the like can only be fired one way as well, and rapid shot can be applied to them, which to me means that you do the same thing you normally would except you have trained to do it faster. I try not to think about how logical this would be by human/physics standards, because everything past level 5 is already supernatural anyway.