As everyone saw in the press already, Facebook bought WhatsApp (maker of the startup mobile messaging app and service) for a hefty $16 billion. There was a lot of armchair analysis done just after the announcement, on how WhatsApp could be worth $16 billion. Here's a blog post (not mine) from the TextIt Blog, written by makers of the TextIt tool for SMS apps, that concludes the answer is Java ME technology (J2ME), and that Facebook bought WhatsApp for $16 billion because the WhatsApp Java ME port is available for feature phones, which if you look worldwide, still outnumber smartphones by a lot (a fact many developers and entrepreneurs overlook to their detriment).
Here's a quote:
So it finally happened, Facebook snatched
So, even though it might not happen the same way for your mobile startup, you might want to consider the analysis by the TextIt blog post, that if you want to think big for mobile, you should consider a Java ME port of your mobile app to make sure you cover the whole market, not just the smaller smartphone (iOS and Android) market. Apparently, Mark Zuckerberg and Facebook did... :-)