Don't listen to the "it's out of control" or "is very due for a crash because it's rising so quickly" stuff. It comes down to a very simple test: do you think that there are significant reasons Bitcoin would or would not gain acceptance as a mainstream currency?<p>A few reasons I can think of why it would:<p>* The current banking system is inherently insecure. If you have an account number and a routing number (written on the bottom of every check), you can pull money. Bitcoin is potentially much more secure.<p>* It's way too difficult to send money today, especially internationally, and fraud is a huge issue. We shouldn't need something like PayPal. Bitcoin solves this.<p>* If you don't have faith in banks or central governments, Bitcoin doesn't require trust in any third party to function. You aren't dependent on any bank.<p>A few reasons it might not:<p>* It requires too much technical knowledge to use and is unapproachable for mainstream users.<p>* It's too tied up with illicit interests and won't break out of that image, leading it to an untimely demise in culture. A fax machine is no use if no one else has one.<p>* There are lurking fatal flaws in the underlying technology. Maybe a blockchain fork is much more possible than currently assumed, or there's found to be an error in the cryptographic scheme.<p>* Mining power ends up concentrated in the hands of few when ASICs are in full swing and transaction fees aren't enough to keep individuals at it, giving power over the blockchain to a few (potentially malicious) actors. There's no guarantee transaction fees will actually pick up the incentive slack.<p>If you think that Bitcoin will ultimately be widely adopted, buy now. $50 / btc is very cheap in that world. If you think Bitcoin will fail, then any price is too much. Any mumbling that "it's doubled in a month and therefore is set up to come back down to earth" is just hand waving.