Brian Snyder/Reuters; Michael Loccisano/Getty Images; Samantha Lee/Insider This story is available exclusively to Insider subscribers. Become an Insider and start reading now. Investing in blank-check companies has made hedge funds big winners in the SPAC boom. Some market insiders are wary that SPAC mania may be bad news for mom-and-pop investors. Insider spoke with a dozen people to understand what's driving the SPAC boom and how it'll end. Hedge funds have been big winners in the blank-check-company mania that's gripped markets over the past year — to the point that some industry veterans are wary of what they're seeing.