Not if it's for bells. Sometimes--if I feel like it--I'll hit rocks for iron, clay, gold and stones--and I'll pick up bells if they happen to come out, but as the best method for making bells, turnips have pretty much taken over. It's faster and you get a ton more in less time than hitting rocks.
I hit all of them every day, it's just become a part of my daily routine at this point. I keep an eye on what the hot items are and depending on the item, I'll go and use up all the materials I've collected so I can earn some extra bells and clear my inventory at the same time.
mhm, usually! I made a little quarry area so all of my rocks are in one place. If I'm strolling by my little rock area looking for fossils, I'll probably give the rocks a good whack too.
Yes. I find myself perpetually needing stones and iron nuggets for DIYs. I want to make sure to get my money rock. Sometimes I get lucky and get gold nuggets, so it's worth it for that too.