Bitcoin is a particular form of currency.

It has tremendous leaks as a currency, but those same leaks permitted it to become diffusely known and used.

The leak is that Bitcoin is a scarce resource. The maximum amount of Bitcoins that will ever exist is already known.
For this reason, the more people uses Bitcoin, the more value it gets. But for this reason, Bitcoin has the property to be a backup of value, because his value will tend to grow.

Let's say that 100 million people start using Bitcoin for small transaction (like buying an online subscription, or a smartphone). The average person would have an amount of bitcoin around 500$ in their pocket.
The market cap would have a value of 50 billion, so as the maximum available bitcoins will be 21 million, this would mean Bitcoin to have a value of  at least 2400$.
As the people using BTC increases, BTC gets more value.

But, why would you spend your BTC today, if tomorrow it's value is likely to be higher ?

This creates a paradoxical situation: An increasing confidence of the market in Bitcoin as a fair and affordable currency, would be linked with a decrease of actual usage, that could cause its value to  decrease.

http://i.imgsafe.org/a81f16d683.png

For this reason there will always be some risk of fluctuations in the value of Bitcoin, and it's very hard to image Bitcoin to become a widespred currency for everyday life transactions.

Steem, dividing Steem Power (commodity, backup of value) and a real currency (Steem) has overcome this problem. While Steem Dollar adds up increased stability.

The users of Steem can increase, without creating any paradoxical situation: more users just mean more value: for every person involved and for the human society as a whole.

Also if today it could seem just a theoretical speculation, Steem could become, instead of just a Bitcoin "killer application", the real Bitcoin killer.