Serious question: Even if Theranos goes down in flames, won't she walk away from this with a fortune? Maybe not quite the fortune she thought, but still many millions?
Performance is all that ends up mattering at the end of the day. Both Apple and Pixar ended up as wild successes - so yes, Jobs could effectively run both (in hindsight).
The futures for both Twitter and Square are not so sure. At face value, seems like a net positive for Twitter and a net negative for Square.