If Goldman Sachs is right, the Great 2021 Retail Investor Stock Buying Boom that has fueled big-time volatility in shares of AMC Entertainment, GameStop and Blackberry is only just beginning.

The investment bank's chief U.S. equity strategist David Kostin raised his 2021 estimate on household net equity buying to $400 billion from $350 billion in a new research note to clients. In the first quarter alone, households were the largest source of equity demand with net purchases of $172 billion.

In one of the clearest signs of exuberance on the part of retail investors (perhaps too much, Kostin estimates that households currently allocate an outsized 44% of their assets to equities. That is only slightly below the all-time high of 46% seen back at the height of the dot com craze (and subsequent blowup).

"High cash balances and continued retail participation in equity markets should bolster household equity demand. The tradeoff households face between equities and other asset classes favors equities through year-end given anemic money market and credit yields. Additionally, any signs of a sustained increase in inflation would favor equities over bonds or cash," explains Kostin.

To be sure, the enlarged appetite to buy stocks among the retail crowd outlined by Goldman is poised to be severely tested in coming weeks.

Renewed volatility has swept through the markets in the aftermath of the latest Federal Reserve meeting, where policymakers opened the door to higher interest rates and the start of tapering bond purchases. Both actions are seen as headwinds to stock prices in the months and years ahead.

The markets didn't appreciate the surprising level of hawkishness from the Fed, and made their views heard.

The Dow Jones Industrial Average tanked more than 533 points on Friday as investors digested fresh hawkish comments from St. Louis Fed President James Bullard two days after the latest Fed meeting. All of the Dow's components finished in the red, led by Chevron, Walgreens Boots Alliance and Goldman Sachs.

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Last week's mostly risk-off environment in the markets highlighted a shift in sector ownership that has been underway in recent weeks to little fanfare among pundits. Most of the best-performing sectors over the past month have been defensives and tech, both of which tend to see strong interest amidst heightened market uncertainty.

Some Wall Street strategists suggest it's time to buckle up as today's market is looking very different than the one earlier in the year.