Instagram and WhatsApp thrived only because Facebook acquired them, else both companies new they would be smothered to death. That pretty much fits the bill of "acquired... Using investment capital and money from first mover advantages".

They don't need you to use your FB account because they cross share data anyways. It's not like it's a painstaking operation to link different accounts, once you have all sorts of device data (which Facebook had, even on Apple devices up until recently).

Much to the dismay of many. Maybe it's the test case FB is monitoring to look how to move ahead with their other acquisitions. Last I heard Quest 2 sales are good..