This past weekend a screenshot went around Twitter (my part of Twitter at least!)
weight = num_items * Max_held_mult; if( weight <= random(100) ) ?label8; print "You're holding too many things already!"; new_line; rfalse; .label8; move noun to player;
(-- @icculus, Aug 26)
The clear reading of this code (as the screenshot says) is that the inventory limit in Zork 1 is random, not a fixed number of items. Each item you pick up makes it more likely that you'll hit a "holding too many things" error. But since it's a random chance, you can just try again -- it might work next time.
This was passed around in a commentary cloud of "This game was unfair," "games in the 80s were terrible," and so on. (See this NeoGAF thread, for example.)
This is fascinating! I played Zork, as I played all the Infocom games, and I didn't remember this inventory detail. It felt dimly familiar when I was reminded of it, though.