You've got a couple of things upside down here...
First of all, a brandname doesn't fall from the sky. It emerges out of something that is related to the name.
So what created the brandname "Bitcoin"? The protocol that is running the currency! If you create another version of this protocol, it is exactly the same thing. Why shouldn't this currency evolve in the same manner as Bitcoin did?
Your example with the Ipad doesn't fit in this scenario, because if you got an Ipad you don't need another tablet and vice versa.
To the contrary, you can put half of your value in Bitcoins and half of your value in Bytecoins. This is even better than only to put it in one currency, because of diversification.
Now, getting back to this hypothetical Bytecoin, what you guys are saying is that this Bytecoin would be able to suddenly overtake a 4 year advantage, overcome the brandname and first mover barrier and get accepted by the same people that accepted BC, getting magically accepted by people and companies whose normal tendency is to to only go with the established brand and then suddenly have a similar infrastructure as BC, where all markets and exchanges decide to denominate their products in Bitcoins as well as Bytecoins, even though we have already seen other digital currencies crash and burn.
This is again the reasoning completely turned on its head.
People don't accept a currency because other people do so, they aceept it because the characteristics of the currency are good.
If they only accept it because of other people, well then this is a very clear sign of a big bubble.
As the characteristics of Bitcoin and Bytecoin are exactly the same, why should anybody accept only one of those currencies?
Further, there is no need for everybody to denominate their products in Bytecoin. If someone doesn't, you can go to the exchange, sell your Bytecoins and get some Bitcoins. This could even be done automatically by payment systems.
And then we haven't even hit the main problem with this hypothetical scenario. The scenario described above would result that this new currency would have a different exchange value. If you try to force the market to have this Bytecoin be the same value as a BC, it would be neccesary to have the exchanges like mtgox incorporate the Bytecoin on their sites. If the exchanges don't accept this, these Bytecoins will be forced to have its own seperate exchange. As a result, you won't be able to prevent the Bytecoin from having a different exchange value. It will essentially be a different currency to BC, and thus couldn't be regarded as being part of the BC supply.
How does the exchange value of a currency affect its acceptance? Do you care if you have to buy 10 Bitcoins to store your value or 10000? You only care about the currency keeping its value. The price is completely irrelevant.