I'd argue Bitcoin could be as legitimate a currency as anything else, but the problem is that it's pegged to nothing. It's value is entirely defined by being a get-rich-quick scheme. Sure, there are plenty of people playing similar games with legitimate currencies, but they're not the ones defining its value because those currencies are still tied to more tangible things.
Even real currency seems to be as ephemereal as digital currency. If bank software tragically moved the decimal place or truncated my savings account balance I could lose practically everything. If someone nefarious creates a substantiating transaction or stole/destroyed the computer, it would be even harder to counter.
Wealth has become a measure of the amount of trust and confidence that people have in each other, beyond the measure of economic accumulation. Wealth indicates how much potential there is. It is losing more and more exactness or precision as more and more people are focused on the pace that they can aggregate their own riches.
Theoretically if this trend is to continue, there would be more instances of disputes and less certainty of what the truth is. There have already been a phenomenal amount of scams. It's a little like Russian roulette with a really large number of empty chambers.
To counterbalance this fuzziness, people will have to build their ability to convince other people to transact goods and services despite the degraded certainty of the value of a dollar. This goes beyond a credit rating. Perhaps people will have to build greater defensive positions, of course, at significant personal cost.
Bitcoin is/was to some degree a "test" of how well the world would operate with a novel monetary system disconnected from authority. The idea seems practical enough, though the implementation was flawed. Even though many computers around the world validated transactions, the need for a central server as well as higher performance computing makes Bitcoin useless to the masses and ultimately limits the potential for owners of Bitcoins.