Bitcoin was and still is an incredibly small market, even at the recent high of about $30 the entire economy had an approximate valuation of about $200 million which is tiny on a global currency scale.

The number of BTC is finite. As more people come to desire bitcoins, that means there are more dollars chasing up a relatively stable number of BTC. Assuming BTC is destined to become widely adopted on a global scale, $30 is still very cheap. There is nothing unhealthy about the present growth, it has had frequent downward corrections as the price has risen; this is indicative of healthy growth. At some point in the future the growth will likely taper off to a more "normal" rate.