One guideline I have for my own game is that if I as DM can't think of (at least) three different ways for the PCs to deal with a problem, it's probably a single-point-of-failure roadblock and needs to be rethought.
Players, lacking the DM point of view, often don't see some or all viable solutions due to various reasons such as imperfect information, having a bad day, misunderstandings, poor communication, missing players, or not being invested in the problem and wanting to go somewhere else.
Conversely, they often come up with completely unanticipated solutions, some of which are so good they just work, some of which have varying chances of success and some of which aren't viable.
Sometimes they come up with something that shouldn't strictly work due to hidden info they aren't privy to, but is so awesome it's worth changing the setup so that it does work.
I find that too many failures drains the morale of players, and may indicate a lack of understanding of the true situation and perhaps a need to discuss things OOC.