If bitcoin is open source software, has anyone modified it to make a slightly different currency?
The supply of bitcoin is limited, but the supply of bitcoin alternatives is very large.
Someone could also develop a currency that many people see as better, and this would displace bitcoin (Ex. friendster got replaced by myspace which got replaced by facebook).
This could stop/reduce the deflation and speculation as people could create new virtual p2p currencies in response to a growing demand for them.
Having multiple currencies would also make it harder for anyone to shut them down.
I think you actually raise a good point. A competing crypto-currency is still seen as one of the really big threats to bitcoin, bigger than bitcoin being declared illegal in a jurisdiction or two imho. It would have to be a very good alternative currency though. It would need to solve some of bitcoins problems, some are know to exist eventually but are not felt now. If another currency could improve on these "flaws/features" and people want it then yes, bitcoin will be replaced.
I think however that unless there is some physical or legal barrier only one currency will survive. The only alternative currencies that might have a chance of coexisting (and maintaining value) with BTC are gold and silver. Fiat currencies might also exist but simply because there will be decrees mandating their acceptance for debts, a mechanism the governments of earth probably won't let go.
It would probably make it harder to shut multiple currencies down, but getting a few functional and up and running that will not tend to want to all meld into one will be challenging.
