'You have to feed the beast. At the end of the day, it's better to be there and engage than it is to not be there and hope you avoid some tough questions,' says president of US think tank, Information Technology and Innovation Foundation
'When major companies testify in front of the Congress it's never a good thing' for their stock price, says a financial analyst
'There's an empty chair next to you for Google, they're not here today – maybe it's because they're arrogant,' says one Republican senator
'We need to seriously think about whether the time has come for these companies to abide by new transparency obligations,' says US Federal Communications Commission chairman Ajit Pai
The US Senate Intelligence Committee's hearing will focus on 'social media companies' responses to foreign influence operations'