How to be a decent GM
We see what develops......
The first and only tabletop game I played was a freeform Dn D game at camp. We made very little story progress despite the GM being a veteran player and 2 of the 5 players being lawful good just to get the turns moving faster. This one kid got picked on by the GM (and by extension, the NP Cs) whenever he whined, leading to a vicious cycle in which his character's wangst took up so much of the story that it crawled to a halt. On the bright side, I got to be a robot (read "warforged") and won a grapple check against a 50 foot spider. That's a pretty good one, right?
And that's a perfect example of what I was just saying, right here! ^^ You got your fun by suplexing a giant spider, and that's all good. Maybe someone else would had fun by taming and riding the beast instead, who knows? But trying to put the other player in the line by force wasn't probably the brightest idea. I didn't touched that in that installment, but that's a reaction most player (especially newbies) have: if things don't go their way, then they'll just blow shit up and make a hard time for everyone.
I do your "Carebear Alternative" all the time. When a player asks to do something stupid, I say "are you sure?"
I think I've heard about an ability from an RPG game somewhere called "Common Sense" that's basically the "Carebear Alternative" as a game mechanic - it requires the GM to inform the player when he's about to do something stupid.
Oh yes, I did see that ability in a few games. Sadly, it usually costs aptitude points that most players prefer to spend on other, more useful powers. But by any mean, go ahead, give newbies that ability for free!