Applying limits : as a large company unravels towards bankruptcy, it's business plans evaporating to ether it rapidly approaches the hallowed title of a startup. By the above metric sun was a startup post 2002, AMD is still a startup, Blackberry is a startup...
Dave McClure makes a fair point that until a company works out the following three things, they're a startup, not a business.
1. What its product is,
2. Who its customers are.
3. How to make money.
So yes, a post-IPO company valued at $21B which still hasn't worked out two of those three items is still a startup in my opinion...