Paul Tudor Jones expresses a bearish outlook on the S&P 500, noting that historical data suggests 10-year forward returns are negative when buying at the current P/E ratio of 22. He warns that a mean reversion to historical valuations could trigger a 30% to 35% decline in equities, potentially causing the bond market to get "smoked" as the budget deficit expands. Additionally, he highlights increased illiquidity risks due to private equity growing from 7% to 16% of institutional portfolios since 2008.