Amateur investors speculating on stocks have pushed markets skywards, but angered some of investing's biggest names. Here's what they have to say about the day-trading boom.

Stocks have rallied sharply in recent months, thanks in part to a boom in day-traders, who invest in the markets for fun, rather than professionally.
Dave Portnoy, founder of Barstool sports turned investor has become the poster-child of day-trading which has helped markets skyrocket, and fuel fears of an inflating market bubble.
Popular online trading platform Robinhood has surged in popularity and generated more than 3 million account openings this year. 
Several billionaires have critici