I'm not so sure the term "bubble" is a good one.
Since Bitcoin is so many things - currency, commodity, payment system, protocol, internet money - you can't make direct comparisons with say; the real estate market or the gold and silver markets.
IMO Bitcoin has several of the qualities of an Internet startup company with new/revolutionary technology. And some startups just keep gaining value until they are multi-billion dollar companies...
The fact that valuation is rising fast does not necessarily imply that there is a bubble.
It seems the current problem with BTC and what's driving the price down is a loss of faith by the public in general in the currency which is due to the inability the brokerages have shown in being able to handle a huge amount of trade.
They've discovered that it's not water tight and everyone but the hardened speculators want out before the thing goes back to 13.85 where it started this climb back in February.
It's a pity that these 'one man band' operations have created a titanium needle for their bursting of the 'bubble' since it could have been strong enough to withstand the sudden global surge of investment capital that it was raising when it 'blasted off' in value two weeks ago,
The major brokers were so swamped they couldn't handle people's requests for funds and this was perceived as as failure. probably true given the Ddos attacks on Mt.Gox and probably the same on nearly every other exchange worth mentioning, all of which showed themselves as just a bunch of amateurs.
'Mt.Gox has utterly proven itself a mountain that doesn't really exist even in cyber space, they couldn't get the rocks piled up quick enough to stand above their circumstances. The first part of this statement is ironic, since the subconscious psychological image presented by the term 'Mt.Gox' implies that it has the nature of a summit, an impenetrable stronghold and some sort of fortress composed of a mountain (implied to be 'golden' from the first two letters of the word 'gold' and the letter 'x' added to denote an exchange. How very far from the truth this now looks.
The future place that BTC will inevitably hold in the global economy can only be achieved when the so-called major players in BTC brokerage can prove they're technically up to speed and as safe as an actual physical oz of 99.999 gold when 10 billion dollars appears in their bank accounts from buy order investors and in a day they can process 20,000 new account orders and still get a lunch break.
Obviously, these days are not here yet and it leaves me to ponder this question, did the well conceived, concerted Ddos effort to quash the exchanges abilities to cater to the needs of new buyers occur in order to deliberately devalue the BTC and cause it to slide out of public favor and, was the source of these attacks not so much 'rogue' forces attempting to deliberately manipulate markets to make for themselves a shady profit, but some high level hacking by those administrations within the G8 who saw the potential for the BTC as a new alternate currency over which they had no real power?
Perhaps inside the TOR network might be the safest place to put the next 'Mt.Gox'? That is, if the major banks of the world (in partnership with the G8 and under a contract with clauses where the ownership of BTC is regulated to include full and open disclosure to those governing bodies of the identities of those who are purchasing BTC and also with the inclusion of equally mandatory, conditional requirement to allow the tracking of the detailed market movements of every BTC)
I wonder if they aren't already arming their IT departments amd the world's largest supercomputer to assist in vending the BTC as the future 'media ordained' 'safe' brokers and take full advantage for themselves of this inevitable slide away from the world's ever crumbling hard currencies?