On the note of bouncing ideas. I have been thinking, "Wow it has been a long time since I have seen puzzles or riddles thrown at a RP group."
As others have said, it definitely can be overdone. A solid, fun puzzle or riddle is good for a group who can get into that sort of thing but there are a few catches.
First, cell phones with internet connections, and laptops have to disappear. I caught a player not to long ago using his iphone to lookup answers to a simple riddle.
Second, You run into the problem where some players want to play their stats, and they personaly may not be a match for it. While a player might not be able to figure out a riddle, a character might be smart enough too, so how do you balance it out? Int based rolls for hints? A time limit, followed by a roll if no one guesses?
I find the best situation for riddles is when there's a strict time limit. They can disrupt the flow of the game otherwise. I played in a game where the GM insisted we figure it out on our own, nevermind a couple of characters had Int's or Wisdom's much higher than our own (not to mention suitable experience) so we sat for over 2 hours bored for most of it.
Ultimately I think in moderation and applied apropriately it's fine. If a player is playing a character with high intelligence, try to make the riddle or puzzle something they may be familiar with - it gives them the best chance of figuring it out.