Hedge funds, small investors and their stockbrokers are bracing for tougher regulation.
The videogame chain’s shares are now worth only a quarter of their high of $483 last week.
Immensely popular 19th-century bucket shops allowed ordinary Americans to gamble on the movement of stocks.
Steve Cohen is seen by small investors as an enemy in the GameStop stock drama.
At least a dozen proposed lawsuits accuse Robinhood of breaching its contract when it restricted trading.
Association chief executive Oliver Mander says New Zealanders trading via apps like Sharesies should look before they leap.
The bold move comes despite fears of an imminent correction.
"There’s going to be some blood on the floor when this is all over."
The tug-of-war has pitted hedge funds and other short sellers against retail buyers, many motivated by commentary on sites such as Reddit.