It might have passed you by, but an essential part of the Internet's infrastructure took a heavy knock last week. The Silk Road—you know, the website where you can buy any drug imaginable—was subjected to a series of distributed denial of service (DDoS) attacks.
Calling the Silk Road "essential" might seem an exaggeration, but it isn't if you're one of its many regular users. The same goes if you're a regular user of Bitcoin—its journey to mainstream acceptance began with the Silk Road, as it's perfect for anonymous, untraceable transactions (as long as you're careful not to make your identity obvious, of course).
Right now, Bitcoin is undeniably a mainstream currency, even if it is not necessarily popular in the sense of being used by a significant proportion of society. But it is viewed as a legitimate method of payment, and a legitimate asset, by the people who matter in these issues—CNBC has it as a ticker on its website, for example, and there's a Bitcoin hedge fund in Malta.