You want to pick something that everyone will be able to use. You may want to think ahead and see what technology is relatively new right now but will become ubiquitous in a few years' time. Mark Cuban stressed this in an interview, and it's why Twitter took off when it did.

Examples:
- Mark Cuban advising people to solve ubiquitous problems: http://www.youtube.com/watch?v=y7sgICX5m0o&t=2m0s
Your Path to a $16B exit? Build a J2ME App
http://blog.textit.in/your-path-to-a-$1 ... a-j2me-app

So it finally happened, Facebook snatched up WhatsApp for the not so bargain price of $16B to the simultaneous head explosion of every entrepreneur in Silicon Valley. A common cry echoed around the world "But, but, how is WhatsApp any different than iMessage / Facebook Messenger / Hangouts?"

To that, I have one answer: J2ME

See, WhatsApp wasn't born in Silicon Valley on an iPhone, rather it fought its way to a $16B exit by providing an awesome messaging experience to the middle billion, those living on $10 a day. And you know what, on $10 a day you probably don't have an iPhone or an Android handset. Rather you are probably carrying around a "feature phone", one of a thousands variations of handsets built by Nokia or Samsung running a version of Java 2 Mobile Edition. (J2ME)

Writing J2ME apps is no cakewalk. While Android developers might whine about having to support myriad resolutions and versions of the API, J2ME ends up being less a standard and more a series of rough guidelines. There is no shortcut, you just have to test on every device, each with its own unique bugs and idiosyncrasies. Building a high quality app aimed at J2ME is the very definition of shlep, it is incredibly time consuming, boring and frustrating work.

That was the genius of WhatsApp really, they recognized that messaging apps are all about network effects and instead of focusing on the comparatively small market of the 'developed world', instead targeted the other 3 billion people who don't have smartphones. And at that they have been supremely successful.

If you are anywhere apart from the States, WhatsApp is the de facto standard for messaging. Here in Rwanda, it has far more penetration than Facebook, it is used by literally everybody who has a capable device. That came about not by having some edgy new user interface, or by a gimmick around disappearing messages, but by providing real value, value that can be measured in the pocketbook of a market that is massively under served.

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