Given their power in mediating human-human communications at every scale, It would be an act of colossal self-harm to allow them to act opaquely and without constraint.
The exact nature of oversight and constraint is an evolving question, but I'm very confident the right answer isn't “none”.
Edit-We’re going through a period of media outlets and whole media segments going bankrupt and out of business. Meanwhile FB is the F in FAANG stocks-amongst the most valuable companies on the earth.
Facebook revenues are EUR 70 B / year, tax receipts in the European Union (EU-28) are around EUR 6,000 B / year. Facebook is a gnat, but the press somehow manages to convince people that the former is a larger threat than the latter because it's not elected.