Bitcoin is not a bubble, because Bitcoin is not simply an asset like gold or other kind of purely speculative financial instrument like derivatives and stocks. It can enter a state of mini-speculation bubbles that will correct naturally, and this is what we are indeed seeing.
Anyone calling "tulip mania" clearly does not understand the fundamentals of the Bitcoin protocol. This is an entirely new financial system from end to end that is taking root in the real world in a viral way, moving out of the garage and into serious business.
April's crash was largely due to the simple fact that MT.Gox, carrying 80% of all BTC trade ON EARTH collapsed under the weight of so much new trade traffic, naturally causing a mass desertion when it came back online. Would you keep your fortune in there after that? The surge was largely speculative, sure, but it wasn't the speculation that crashed the price, Gox and its incompetence did. THe Bitcoin sphere has grown a lot since then, many new exchanges now larger than Mt.Gox, new payment systems, mass media exposure that only increases with the market price, and so on. This is a very different situation now. It will never crash on that level ever again I think (though never say never). You can see on the charts that the volumes around April are now substantially higher than the averages now on Mt.Gox as it is no longer the only big exchange. Mt.Gox started lagging horrendously 2 weeks ago, to which the rest of the worlds exchanges shrugged and moved on.
I also wonder what happens to an item that has first, a finite supply (21 million total) and second, becomes incrementally more difficult to produce as time goes on (mining)? I can't help but believe the price will increase as we approach these two facts.
As the saying goes "The trend is your friend, until it isn't" :-)
Bitcoins total coin supply may be 21 Million, but each coin's wealth can be infinitely divided by simply moving the decimal over a place, which is already built into the protocol if needed someday. Really "1 Bitcoin" is a formality, as each is really 100 Million satoshis. The entire Bitcoin economy could theoretically still function even if there was just 1 coin left. Not to say that is practical, but possible. One cannot think of Bitcoin in a fiat mindset, it works very differently than fiat money does.