It's because Stellar cryptocurrency is on fire. You signup at Stellar foundation and they give you 10 dollars worth of this coin, then, you can exchange this to BTC in pages like Justcoin or BX. So.... in the las 10 days, a huuuuughe number of people are getting 10 dollars worth of BTC. Since you need a legal facebook account to get this 10/12 dollars, a lot of people using his girlfriend, family and friends facebook accounts are getting a lot of BTC. A bunch of them from Taringa! (www.taringa.net), there is a big community of gamers and traders, 99% from South America (like me).