This kind of ties into this:
So that's why they all move along. It also happens because when the coins start rising people start panic-buying and try to buy the cheapest or next best coin, and obviously this inflates the price, but can lead to crashes when the excitement has calmed down.
It is quite possible to mine some of the cheaper lesser known coins then trade them for another currency. It's also possible to mine a newer coin then sell them on ebay for a ridiculous premium, if you're willing to take the risk of using it. Just look at the prices of Dogecoin and Sexcoin and Infinitecoin on ebay. The coins are currently practically worthless, yet they can go for hundreds on ebay. It's nuts.