buying 4 house's is putting all your eggs in one basket, to assume that the poster also has $1mil of shares I think would be the gross assumption.
even buying house's in different suburbs is still putting your eggs all in one basket, this is just hedging your bet, protecting yourself from 1 bad egg buy having a few.
dont forget all suburbs have tripled in price in the last 11 years well ahead of inflation.
Buying different suburbs is no different to investing $100K accross 3 oil companies instead of jut 1, so if 1 oiler goes bad you still have the other 2, however you are still effected by the price of oil as a hole, if it drops so do all your stocks.
not putting your eggs in 1 basket means spreading the risk around different investments