While it's impossible to predict the future or even identify market tops, there are a number of troubling signs that suggest stocks are too high. I discuss three of these in the video below, including the absolute level of the S&P 500 (SNPINDEX:^GSPC), valuation expansion over the last year, and the overexuberance of investors in the recent IPOs of Potbelly (NASDAQ: PBPB) and Noodles & Co. (NASDAQ: NDLS).

John Maxfield has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.