Facebook today made waves when it announced a $16 billion deal to acquire the mobile messaging app WhatsApp. Yes, you read that correctly, that's billion with a capital 'B.' That's an absolutely jaw-dropping figure, and far exceeds the $1 billion Facebook paid for Instagram and the rumored $3 billion it offered to Snapchat.

WhatsApp was originally founded in 2009 by Brian Acton and Jan Koum, both former Yahoo engineers. What's particularly interesting, if not downright inspirational, is that Acton -- himself a former Apple engineer -- applied for jobs at both Twitter and Facebook way before WhatsApp became a wildly popular mobile app. Both times he was rejected.

First up was Twitter.

Got denied by Twitter HQ. That's ok. Would have been a long commute. — Brian Acton (@brianacton) May 23, 2009

Three months later, Facebook also told Acton, "Thanks, but no thanks."

Facebook turned me down. It was a great opportunity to connect with some fantastic people. Looking forward to life's next adventure. — Brian Acton (@brianacton) August 3, 2009

And joining Acton as a Facebook reject was Koum, who also interviewed there and wasn't offered a job.

Take heed, kids. Keep on truckin'.