Bitcoin rocketed past the $19,000 mark Thursday morning, before falling sharply to $15,000 around where it stayed for most of the afternoon. The surge continues what's been a remarkable week for the digital currency, which broke $13,000 Wednesday. Bitcoin now has a market value of more than $270 billion, per CNBC, meaning it would rank among the 20 largest stocks in the S&P 500.

Why it matters: Bitcoin, which began the year below $1,000, has had a wild streak in recent weeks, leading Wall Street to jump into the ring on Friday. And while some currency experts warn that the Bitcoin's recent price surge has created a bubble, others argue its success is due to delayed recognition by the broader financial community that cryptocurrencies are becoming mainstream.