Yes, because a bunch of people deciding that they need a GoPro that they'll never use or drop extra money on a fashion line that has some celebrity's name on it

Yes, because a bunch of people deciding that they need a GoPro that they'll never use or drop extra money on a fashion line that has some celebrity's name on it isn't a big deal. That is money that is gonna be spent anyway. Sending irrational ripples through the stock market affects things like interest rates, retirements, and employment in a somewhat widespread manner.