Okay, former Rare members split off to make their own successor to Banjo-Kazooie but it came out average. Keiji Inafune split from Capcom to make Mighty No. 9 but it came out awful.
This has likely led to people thinking veteran developers shouldn't split off from their companies because it doesn't work out like it should.
However, they forget that in the past it has worked. :)
EX: Former Konami employees who left that company for Treasure, and made great games like Gunstar Heroes. Also Free Radical Design, who gave us the beloved Time Splitters games, were former Rare developers. Then there's the team who made the Metal Slug series, made up of ex-Irem developers.
That's just a few I remember, but who here knows of other times splitting off from an older game company to start your own worked?