This isn't right. The return on capital must exceed the cost of capital, at the very least the market rate of interest. Otherwise you're not taking into account opportunity cost.
I have another issue with your analysis. It's quite blinkered, focused on immediate profits with the zeal of an accountant. Solutions to the photo problem have potential for being strategic, and I don't think it's been figured out yet.
A better focus on cost structure could have extended the lifetime of the company, but it likely would have grown too slowly for "$B". I think the founders tried hard to generate growth metrics, betting that the growth would convince investors they could hockey-stick. But they didn't get quite enough growth, and their burn rate was too high to put on the brakes[1] - and likely they weren't interested in putting on the brakes. So I don't think your analysis is particularly relevant in the end. It deals mostly with cash-flow level tactics, whereas this was a strategic play.
Don't get me wrong, I think you're a decent analyst. But I expect people use you for your specific focus, not for the big picture. I think you would have predicted YouTube to be a failure, for example.
[1] I'm relying on the burn rate being in a vehicle of some sort for this not to be a mixed metaphor...