Hitchhiker’s Guide might be one of the cruelest Infocom games in this regard. In particular, if the player fails to perform a particular action involving the dog at the start of the game, the game becomes instantly unwinnable, and the player almost certainly won’t realize it until far, far later. Quite frustrating.
Thinking back to when I played most of these and the Scott Adams ones as well, it was the very fact that you almost expected to wind up in a dead end or unwinnable situation that gave them their appeal. The only helps were either a dialup BBS service or various magazines. But despite all this, I did manage to complete them. I still don’t know if I missed any in-jokes or alternate endings along the way, but I enjoyed playing them then, and still do when I get the chance. How many others of the ‘modern era’ IF have this quality thats makes you want to play them again and again?
Also, although it’s not an Infocom title, let me give props to the excellent TADS game “Perdition’s Flames,” which was specifically designed so that it could not be put in an unwinnable state. It’s still plenty hard and satisfying, though.