Bitcoin as the most popular of crypto currencies does seem to be involved in a price bubble. In my opinion, this is because Bitcoin has recently lost its intrinsic value, and therefore people are only investing because they believe the price will continue to go up, very similar to the tulip mania price bubble, that popped when the individuals involved released that the tulips didn't have an intrinsic value.
Bitcoin, as it stands, doesn't have the value that it once did of being a relatively friction-less and cheap way of exchanging money. At the moment, it costs roughly £3 to send a bitcoin transaction, making it no better than existing options. This doesn't look like it is going to change, as the capacity of the network isn't going to increase much. The bubble will pop, but who knows when.