Updated

Throughout the modern presidency there has been an unspoken, and generally observed, awareness of the impropriety of criticizing a private sector company from the bully pulpit of the Oval Office. That was thrown out the window with the Trump presidency.

More than 17 times via Twitter and a few more occasions in plain-spoken English, President Trump has lashed out at Amazon, the company that has revolutionized the way America goes shopping.
He has blamed it for alleged abuse of the tax system, the postal service, and for ruining main street America.
"You have retailers all over the United States that are going out of business. You look at some of these small towns, who had a beautiful Main Street with stores – the stores are all gone," he said on Tuesday.

Throughout the presidential barrage, Amazon owner Jeff Bezos has remained silent. Only when Trump accused the Washington Post, also owned by Bezos, of lobbying for Amazon did Post Executive Editor Marty Baron respond, telling the New York Times that Bezos has "never suggested a story to anybody here, he's never critiqued a story, he's never suppressed a story."

A larger question surrounds the legal and ethical boundaries of such private sector badgering.
"I think the president is perfectly within his power," said Republican consultant Brad Blakeman, a member of President George W . Bush's senior staff.
But Blakeman adds this caveat.
"Ethically, the president has an obligation not to intervene in commerce because of the ramifications it can have vs. the stock market."

Amazon lost $53 billion last week after Axios reported the president was “obsessed” with regulating it.

Conflict of interest considerations were also raised Wednesday at the White House briefing, when Press Secretary Sarah Sanders was asked about Amazon's bid for a new Pentagon cloud computing contract.
"The president is not involved in the process,” she said. “(The Department of Defense) runs a competitive bidding process."

Radio talk show host Mark Levin, a frequent Trump supporter, told his 7 million listeners Wednesday night that the president is wrong to criticize Amazon.
"Can imagine where we would be today if this mindset had set hold before the Industrial Revolution," he said. "What the hell is this oil stuff? I'm in the horse and buggy business. That's not fair, putting people out of business. And what are these cars?"

His new economic advisor, Larry Kudlow, on Wednesday defended the president's focus on Amazon.
"I think the president's intent here is to develop a level playing field between online retailers and land-based retailers with respect to taxes and other issues," he told Fox News.

Other presidents have not been immune from playing private sector favorites, as when President Obama targeted Staples.
"When I hear large corporations that make billions of dollars in profits trying to blame our interest in providing health insurance as an excuse for cutting back workers’ wages,” he said in 2015, “shame on them.”