Its Not Worth the Paper It's Not Written On!
This is probably the easiest entry that I will ever make on this website, but as I am writing this before I have laid out an investment philosophy I need to make it clear why these do not constitute an investment. The value of a crypt-currency can be established and as such we have the classic exit strategy, that you need to find a bigger idiot willing to pay more for these than you did.
A currency issued by a government is backed by the full faith and credit of that sovereign nation and its ability to raise taxes. There is no such value for any crypto-currency, it relies solely on the holders of that currency believing that it has value.
Crypto-currencies have largely been developed to facilitate illicit transaction and for people to shirk they responsibilities in paying taxes. Driving the value of such currencies up, funds organized crime and terrorism. The volatility that it has experienced in the last year, has provided a haven for money laundering.
The spike in the price of crypto-currencies is fueled by hype and as with most bubbles a fear amongst "investors" missing out.
I truly expect at some point, possibly with the creation of crypto-currencies through central banks, the independent crypto currencies will be displaced, possibly surviving only as the currency of choice on the dark web.