Hi there - Ayo from Hipmob here. You raise a fair question - we believe we can handle the scale challenge well (we're built on Heroku & AWS), and we've deployed with that in mind. That being said, only time (and deployments) will tell.
I'd love to know, for example, how a company like MixPanel or GinzaMetrics goes from handling a few million data points per customer, to perhaps billions. It seems like making the leap from helping other startups to helping Disney could take not just exponentially more resources, but a whole different architecture.