By that logic, you can say the same thing about pretty much every single silicon valley startup.
No cryptocoins will be around for a long time. They are all going to crash to near worthlessness, including Bitcoin and Ethereum.
Also the idea of Webvan was not a bad one, they were just too early. People put too much money in too early to a good idea.
Cryptocoins are not an idea before its time or of its time. It is inherently a worthless thing. Just like quack medicine was worthless a century ago and is worthless now.
Note: I do think bitcoin has value for illegal transactions but that's the only place I see cryptocurrencies solving a problem more efficiently than current solutions.
Why?
> Cryptocoins are not an idea before its time or of its time. It is inherently a worthless thing
That's not true. Coins do things you can't do otherwise. Instant peer to peer value transfer over the internet for example.
You can't do a value transfer when there is no value.
Fortunately for Bitcoin, there is value. And as long as people continue to derive value from its function, it will continue to deliver it.