Facebook has not been harmful per se but like all free communication system it has enabled dangerous ideas to spread. The radio used to do that, television less but still some. But simple leaflets in the old days did that or speakers on Hyde Park Corner in London or in cafés, pubs, saloons, etc, when cafés, etc, were some kind of forums.
The financial hazards will be addressed by those concerned if their power depends on their ability to redress them, at least in elections. Ask voters in Richmond and consider the signal they sent to Downing Street. And strangely enough this time it is the financial people in London who are providing the ideas necessary to stop Superhavoc in Great Britain.
I must say tabloids and the press in general in England are the first vector providing television and Facebook with the raw material they need like the accusation leveled against the High Court Judges by some popular papers.