I've been playing an interesting game as of late where about a dozen players participate in a goods-trading economy. The economy is small, and money values, though they can of course be fractionalized to the hundredths digit, are also generally small (each player tends to start with about 200).

It's interesting to observe, over and over again, how an economy that size will just seize if only one or two players become someone whom everyone wants something from but they want for nothing. Money just pools in their coffers and since they never spend it, it's just gone from the economy. Eventually, people struggle to conduct basic transactions because the amount any individual is holding dips too close to the minimum fractionalization threshold, nobody can afford anything in the market place (except, of course, the one or two players who never spend), and what trade happens happens on a per-unit bartering basis (massively inconvenient given players in different timezones) or not at all.

... fortunately, global-scale economies are far more immune to this effect; with millions more players, millions more categories of good, and far more currency in cycle, such a seizing is basically impossible.

... unless the disparity between median holdings and maximum holdings is proportionately similar to that 200-a-person economy and the few who have all the money can't (or won't) spend it fast enough to keep it in circulation, perhaps...