Virtually everyone's 401k is overexposed to these companies due to their insane market caps and the hype around them. If they go every S&P 500 and total US market ETF goes with them, right as the Boomers start retiring en-masse.

Even Vanguard's Total World Index, VT, is roughly 15% MAG 7.

That's not even getting into who's financing whom for what and to whom that debt may be sold to.