NBC reports that two Twitter employees have been charged in the Northern District of California for spying for the Saudis.
Saudis recruited Twitter workers to spy on critics of Saudi regime, U.S. charges [...]
Ali Alzabarah, 35, of Saudi Arabia, and Ahmad Abouammo, 41, of Seattle were Twitter employees. According to the complaint, between November 2014 and May 2015, Ahmed Almutairi, 30, of Saudi Arabia, and Saudi officials convinced the two men to use their employee credentials to access nonpublic information about the individuals behind certain Twitter accounts.
The Saudis sought email addresses, IP addresses, and dates of birth for individuals who had published posts deemed by the kingdom's royal family to be critical of the regime, according to the complaint. [...]
Alzabarah, Abouammo, and Almutairi, who is also known as Ahmed Aljbreen, were charged with fraudulently accessing private information and acting as illegal agents of a foreign government. [...]
"The criminal complaint unsealed today alleges that Saudi agents mined Twitter's internal systems for personal information about known Saudi critics and thousands of other Twitter users," said David Anderson, U.S. attorney for the Northern District of California.
As the BBC explains the charges a bit better, only one of the three is a US citizen. That article also says that, apparently, it was the first time that Saudi citizens are charged with spying within the US.
I'm aware that some Russians, allegedly working for their Internet Research Agency, have been charged for attempting to interfere with US elections and institutions, but those charges didn't include any US citizens as co-conspirators, i.e. the US citizens the Russians were in sometimes contact with were described as "unwitting" participants in the legal documents. So the recent Saudi-Twitter case seems to go beyond that level, as far as US citizens' involvement is concerned.
So, have any other US social media employees been charged for espionage (or "active measures" like being foreign interference agents) in the US before?