Another blogger reminded me of something: the various treasure sharing methods listed in the 1e PHB. They're in an appendix, so technically not part of the main rules; several options are available, including "one share per level".
As a GM, of course, I stay out of treasure shares. My job is to stock the treasure, not divvy it up for you. As a player, I never bothered with a formal system of treasure shares; normally, we just use one share per character, but in a rough form, with maybe some people passing on divvying up the copper, and magic treasure given to whomever, based on appropriateness rather than fairness. Shares for NPCs, and maybe even for PCs, may be based on negotiation rather than meta-level game rules.
That seems more natural to me; after all, we're pretending to be people in a real low-tech magical world. "Level" certainly represents a concept within that world, but doesn't have an in-world numerical value, so we would never use it as a way to distribute treasure.
Besides, as a formal *rule*, level-based treasure share systems are an example violating my principle of "rules should make things happen in the game world". Adding the complication of number-crunching levels doesn't make anything extra happen in the game world