One market expert says America's hottest investment product is a bigger bubble than the dot-com crisis — and he's convinced the crash will be worse this time

· Exchange-traded funds are fueling a market bubble that will be more damaging than the dot-com bust when it unravels, according to Steven Bregman, the founder of Horizon Kinetics.
· He says the adjacent rise of passive investing strategies has put much of the market's value in the coffers of a few tech companies. 
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