The sell-off in Wal-Mart stock on Wednesday following an announcement that the company expects full-year revenue to be flat and profits to fall in fiscal year 2017 represents a "massive tipping point for e-commerce," Founders Fund partner Geoff Lewis said.
"People in the technology industry have been predicting that brick-and-mortar-based businesses like Wal-Mart are going to end up really struggling, and I think that that's actually now coming to the fore in this powerful way today," he told CNBC's "Squawk Alley."
"It always takes longer for these things to shift than people expect, but once they do shift, as Wal-Mart certainly has today, it happens very quickly."
Shares of Wal-Mart plunged as much as 9 percent on Wednesday, as the company shed more than $20 billion in market capitalization at the stock's low.
Read More Wal-Mart falls 9%, wiping out $20B in market cap, on sales guidance
To be sure, Wal-Mart said 75 percent of its forecast reduction in earnings for 2017 will be due to its investment in wage increases. But it also said it would invest about $1.1 billion in fiscal 2017 to compete on e-commerce and digital platforms with rivals like Amazon.
Amazon surpassed Wal-Mart as the world's largest retailer by market cap in July.
"If you want somebody really to blame, you can blame Amazon, because Amazon is forcing the likes of Wal-Mart and Target to catch up, particularly with their e-commerce spend online, and as well, to make the stores more compelling," Stacey Widlitz, president of SW Retail Advisors, told "Squawk Alley."
Former Office Depot CEO Steve Odland noted that Amazon is growing 77 percent while Wal-Mart expects sales to be roughly flat this year.
Read More Wal-Mart just made things worse for everybody else
"That story tells it all. They're getting killed by the Internet and they don't have any choice but to invest this billion dollars into trying to create their e-commerce business," he told "Squawk Alley."
Wal-Mart is not simply spending on technology. It's also increasing expenditures on initiatives to bridge its physical and digital operations.
CEO Doug McMillon told CNBC's "Squawk Box" prior to the announcement on Wednesday that Wal-Mart would hire about 3,000 managers to assist in its expansion of a service that allows customers to order online and pick up products in stores.
Read MoreWal-Mart's McMillon: Investments in stores, tech will help us win
Much of Wal-Mart's technology investment to date has been focused on driving efficiencies around inventory management, supply chains and logistics, Lewis said. While the retailer has been "among the best in the world" in doing that, the company has extracted all the value it can from those back-end improvements, he added.
"At this point, the technology investment that they need is one to drive growth, to drive sales growth with consumers, and they are sort of massively handicapped on that score," he said.
The company now must contend not just with Amazon, he said, but emerging private e-commerce firms like Wish — which Founders Fund is invested in — and Jet.com.
—CNBC's Jacob Pramuk contributed to this story.