Some would argue there is almost no such thing as an “easy trade,” but over the past couple of year, shorting volatility has come close.

Over the past two years, the VelocityShares Daily Inverse VIX Short-Term ETN (NYSEArca: XIV) and the VelocityShares Daily Inverse VIX Medium Term ETN (NYSEArca: ZIV) have each more than doubled. At the close of U.S. markets on Oct. 28, XIV was a $1.4 billion ETN. ZIV, though far smaller, can at least say it is well above the $100 million in assets under management mark with nearly $144 million in assets. [Shorting Volatility Works With These ETNs]

XIV “ has more than doubled in size since the start of October. It crossed over the $1 billion mark for the first time ever on Oct. 16 and peaked on Oct. 21, at $1.33 billion, according to Morningstar,” reports Chris Dieterich for Barron’s.

If some hedge funds are right, the pleasantries afforded to short volatility ETNs could end in sour fashion. Just as some traders and investors are rushing to short volatility with XIV, ZIV and rival products, hedge funds are upping their bets on increased volatility.

“For the first time since 2011, the balance of futures owned by hedge funds and other large speculators on the Chicago Board Options Exchange Volatility Index represents wagers that equity turbulence will increase,” reports Callie Bost for Bloomberg, citing Commodity Futures Trading Commission data.

That could be a sign those daring enough to be involved with volatility ETNs should not be deceived by inflows to XIV and ZIV and departures from long volatility ETNs such as the iPath S&P 500 VIX Short Term Futures ETN (NYSEArca: VXX).