Remember when Silicon Valley was a force for good? With their young bosses, origins in garages and revolutionary products, US tech companies were worshipped for bringing information, choice and innovation to the world.

As reporting season for the US tech sector revs up this week the sheen has come off as campaigners, politicians and the wider public have asked questions about the darker side of the digital revolution. Facebook, Amazon, Google’s parent, Alphabet, Microsoft and Apple are all reporting in the next couple of weeks.

Misuse of people’s data, aggressive tax avoidance, treatment of workers, enabling hate speech and the sheer size and power of the tech giants are all in the spotlight. The US government is conducting an antitrust review and Elizabeth Warren, the new frontrunner for the 2020 Democratic nomination, has pledged to break up the digital monopolies.

Amazon, which reports third-quarter results on Thursday, is a case in point. Jeff Bezos’s company has faced repeated questions about working conditions at its warehouses in the US and the UK, where it is running an ad campaign featuring happy workers. Critics hold it partly responsible for the crisis on the high street.

Amazon’s sprawling business – from retail sales and computer gaming to advertising and entertainment streaming – is in Warren’s sights and in Britain the competition authorities are investigating its investment in Deliveroo. It could also be affected by proposals to make big tech companies pay more tax in countries where they make sales.

The Seattle-based company has told investors to expect third-quarter sales to jump by as much as 24% to a maximum of $70bn as it piles on revenue from cloud computing and its Prime service’s one-day delivery offer. Operating profit, though, is set to fall from $3.7bn to between $2.1bn and $3.1bn as Amazon spends on transport to expand its fast delivery offer.

Amazon’s shares have fallen by about 10% since disappointing second-quarter results in July as investors digested its heavy spending message, amid general wariness about the tech sector made worse by dud share sales by companies such as Uber, Lyft and Slack.

Neil Campling, head of technology research at Mirabaud Securities, said: “There is an overhang on big tech at the moment which is weighing on Amazon. You have got very high expectations and companies with very high valuations, and when a sector is priced for perfection that creates extra risk.”

The shares are worth more than six times what they were just five years ago and Wall Street analysts reckon there is more to come. The company has so many irons in the fire that it’s hard to understand what’s going on. Supporters have to believe that its size, ability to invest and Bezos’s relentless focus on keeping customers happy is a magic combination.

Andrew Murphy, managing partner of US tech investor Loup Ventures, says Amazon is still a high-growth company because of its willingness to experiment, and will escape a forced break-up despite its size. “While they’ve demonstrated the capability of turning on the profitability spigot at will in a given quarter, they are still in investment mode,” Murphy said. “Amazon will experiment and spend to test seemingly anything.”

Is Amazon a risk-taking innovator or a relentless sucker up of other people’s business? Campling points out that Amazon’s cloud service supports many other companies, “creating an economy of its own”, but adds that Amazon can use the information it gets from the service to move in on the next trend.

“Amazon is affecting every part of our lives,” Campling said. “Some people will think it’s the devil and others will think it gives us choice.”