Palantir has been one of the top stocks in the S&P 500 in two straight years, but it's also one of the most expensive software stocks in history.Palantir Technologies (PLTR 1.78%) is one of the top five stocks in the S&P 500 (^GSPC -0.55%) for the second consecutive year. Shares have increased 135% in 2025, which is particularly impressive after the stock advanced 373% in 2024.However, many Wall Street analysts view Palantir as overvalued, and history says the stock is likely to fall sharply at some point i ...