In my personal experience, I first heard of it 1 year ago in a online forum game, people sold gold for Bitcoins, around March, gave it no importance at first. Now im kinda utterly commited to it. Really an interest subject of study.
Where did i first hear about, i heard it on cnn news on around 2011-2012 about cnn news debate on bitcoin and the anchor said that the bitcoin is worth nothing but now looks its getting higher and higher.