Alphabet shares close down 13%, $479B in market value wiped out

A single-session loss of this scale at a mega-cap is a reminder that concentration risk cuts both ways: the same handful of names that carried index returns can erase value faster than diversification can absorb. The read-across matters most for passive and index-tracking exposure, where Alphabet's weight transmits the drawdown to holders who never made a direct bet on the company. Whether this proves an isolated repricing or the start of a broader de-rating across large-cap tech is the open question worth watching.