a case is stupid because who wears a case on their normal watch? Nobody. You expect your watch to handle normal life's wear and tear. So should the apple watch. To be fair, Apple haven't suggested a case, it is just the smartphone accessories world jumping on things. People shouldn't be treating it like a phone, its a watch.
And a waterproof case is stupid because the watch should be waterproof in the first place.
It is not a normal watch tho. I never used a case on a Nokia phone... and I also never used a case on my iPhone 3GS, and barely used one on my 4 (got a free one due to antenna-gate which I used sometimes until I lost it). But I use an Apple leather case on the 5. Because it looks and feels cool, and it adds protection on top of it.
The bottom line is that, it doesn't matter if it's watch, phone, tablet or whatever. It's an Apple product. Apple products typically have a myriad of third party (and sometimes 1st party) manufacturers doing all kinds of accessories within a wide range of price, taste and usefulness.
If it's a watch and you'll not treat it like a phone, will you not charge it every night then? Right. It's its own unique product, and people should not be bound by what category it should fall in so we follow some sort of holy word of how it should be used.
I'm not getting a case myself when I get the Watch, bar, say, an waterproof one for vacations if I think it's a good deal. And I agree, it should be waterproof. I expect that to happen within 3-4 generations.