Investors are cooling to one of the hottest bets on Wall Street as new regulatory scrutiny of special-purpose acquisition companies cuts the flood of new issues to a trickle while share prices tumble. Critical comments from regulators appear to be scaring off some investors and new offerings. Until last month, roughly five new SPACs hit the stock market every business day in 2021. In the past 14 days, 12 new SPACs have started trading, SPAC Research data show.