[sgornick]

To be a proof-of-work based cryptocurrency, it would need to make it through the phase where it is vulnerable to external attack.

Bitcoin made it through because nobody knew that a proof-of-work based cryptocurrency would ever end up being worth several hundred million dollars or more.

Now that bitcoin exists, any competitor risks getting spanked down. Even bitcoin is at risk of getting spanked due to a 51% attack, except that it will cost more than $10 million in hardware to do that.

One alternative is using scrypt instead of sha256(), and thus GPUs aren't as effective and the one crypto currency doing that has avoided attack thus far. That currency is worth under half a million dollars of valuation at the current exchange rate and there are hardly any exchanges where it is traded so there's little financial gain from attacking it sooner rather than later. But it is still very vulnerable, in comparison to bitcoin.

[adrianwaj]

A bitcoin2 should be a swap currency. 21 million coins pre-issued, and sold for 1 btc each. Like when a fiat note is upgraded, the old note is eventually taken out of circulation and destroyed. But how do you trust the issuer of bitcoin2 to destroy the bitcoins they receive, and that they won't issue more bitcoin2s for themselves later secretly?

(or they can just lock the bitcoins they receive for guaranteed swap-back at any point later - the bitcoin2 issuer is a bitcoin bank too: how do you trust they can effectively lock them up with the possibility of return later?)