The are some "classic" signs of market bubbles in certain asset classes, according to VTB Capital's Global Macro Strategist Neil MacKinnon, who believes that easy money from central banks is to blame.
"I think what we're seeing across some asset classes is the appearance of bubbles — we're thinking of cryptocurrencies," MacKinnon told CNBC Tuesday, also mentioning the market for fine art. "There are bubbles and I think they arise from ultra-easy monetary policy that has created a speculative excess and excess leverage."
MacKinnon is not alone in this view — many market commentators have warned of the downsides of enduring loose monetary policy, calling for an end to quantitative easing in the face of resurgent global growth.
"There is growing concern among some market commentators, even among central banks, that there is a potential threat to financial stability," he went on. "I think the (Federal Reserve), for example — they are concerned about the risk to financial stability, and they should be."
The Fed has forecast three rate hikes in 2018 while targeting a range of 1.25 percent to 1.5 percent for its benchmark interest rate, inching up from years of historically low rates as economic growth strengthens.