The money to be considered "coin" should have 3 qualities:

* Be considered an instrument of change:

a) People with bitcoin can exchange it for products/ services.

b) People with services/ products can exchange it for bitcoins

* Be considered a means of payment:

If there were no coin, one would have to have two matches. (if I sell a service, I would need the other one to have a product I wanted and the other way around). If a coin is accepted as a means of payment, the seller would be satisfied by receiveing the payment. The acceptance of the coin is based in trust and habits. The coin has the quality of liberating debts.

* Be considered a means of Value Reserve:

You can store it now and spend it later. People will store money with intentions of transaction, safety and speculation.

I think Bitcoin has the qualities to be considered coin.

A coin would be more usefull for society if its value is stable, as people could predict investments and offer products and services. So, it is a question of more people using bitcoin.