> So any change in the smaller companies is dwarfed by one good (or bad) day of AAPL, AMZN, GOOG, etc (as happened yesterday).
This doesn't seem that bad to me?
Imagine that you own FOO and BAR. They're each 1% of your holdings and each 1% of the US stock market. Now they merge. How much of your holdings should be the new company FOOBAR? Seems to me like it should be 2% now that FOOBAR is ~2% of the market.
AAPL, AMZN, GOOG, etc each represent a large number of products and businesses, and I don't see why you'd want to decrease your exposure just because they trade under a single stock symbol.