I know the Cisco UC teams directly and Zoom Engineering as well. Cisco and Google just can't stand that so much money have been spent in acquisitions and engineering that a smaller company just beat them in the consumer and enterprise space (Cisco acquire Tandberg, Latitude, WebEx, defuncted Jabber and some of the Telepresence technology), same as Google (creators of WebRTC and few apps Hangouts, Meet, Duo, etc) that a small company beat them badly, that's the reality. Yes some Zoom Engineering is in China, so what? Unless you have solid technical proof that there is a security problem, is just gossip and bad press, I though this is a technical forum
Actually, I don’t think that zoom have any kind of technological improvements than the other companies you mention, as Jitsi proves, making a videocall and screen sharing app it’s not really very difficult, as the building blocks are already stablished and it’s a matter of how you join them. Zoom make the choice to try to circumvent some security things to be able to appear less hostile for the user, and it seems that it was worth it. Several other things (integration with third party calendars, conference and seminar tools) are the ice in the cake.
