In the second quarter of 2006, Amazon's operating income plunged 55% year over year as the company prioritized Prime and its nascent cloud business.

Amazon.com investors are currently enduring a brutal selloff, the likes of which haven't been seen since the company was still primarily known for selling books and CDs.

Shares of Amazon (AMZN) officially recorded their ninth consecutive day of losses on Friday, closing at $198.79. The stock is down 18.2% over this period, which marks the longest losing streak for Amazon's stock since July 2006, according to Dow Jones Market Data.

For context, that was the year Amazon launched its cloud-computing platform Amazon Web Services - a decision that many investors criticized as being too expensive and margin-shrinking, with no visible return on investment at the time. Some wondered if then-CEO Jeff Bezos had "finally slipped off the deep end."

It was also the early days of Prime, and to many investors the membership program was a massive waste of money. Prime launched in 2005; by July 2006, shipping costs and technology spending led Amazon to report a 55% year-over-year decline in operating income for the second quarter of the year.

Almost 20 years later, the same complaints are back. CEO Andy Jassy announced on the company's most recent earnings call that it will need to heavily invest in AI infrastructure to meet booming demand for AWS. Now, investors are concerned that Amazon's $200 billion of planned capital expenditures this year will burn through the company's cash reserves and require it to take on debt. Elevated capex levels also present the risk of saddling Amazon with depreciating chips and servers that will send expenses soaring in future years.

Friday's decline came after Amazon's stock fell into a technical bear market on Thursday, becoming the second "Magnificent Seven" name to do so this year after Microsoft $(MSFT)$.

For Amazon and the rest of the Magnificent Seven to calm investor concerns about overspending, they will need to show a tangible return on investment. But these returns could take many years to appear.

Amazon first reported AWS-specific financials starting in 2015. By the first quarter of 2016, AWS was more profitable than the company's entire North America retail business, despite generating less revenue. Today, annual AWS run-rate revenue is $142 billion.

Jassy's message to investors on the company's Feb. 5 earnings calls was to be patient. "This isn't some sort of quixotic top-line grab," Jassy said of the company's AI investments. "We have confidence that these investments will yield strong returns on invested capital. We've done that with our core AWS business. I think that will very much be true here as well."