There is only one way to make me completely uninterested in cryptocurrencies: if the big one gets phased out and a "next" one takes over. I would lose all my trust in the concept, knowing that my coins will lose value when a newer currency comes out. I want there to be just "one", otherwise its just a shit show. If litecoins, ripples, zerocoins, or shitcoins ever pass bitcoin, then thats the day i stick solely with fiat money.. there's enough "play" in this game as it is, competing cryptocurrencies will just chase me away if this gets out of control.
Zerocoin is NOT an alternative currency. It is a proposed extension to Bitcoin to solve the lack of anonymity in Bitcoin transactions. Since all transactions of every Satoshi ever spent is recorded in the blockchain, you can imagine how easy it is to map out the connections, deduce owners, and see who has how much, and where it went. It is like a built in mixing service.
The Zerocoin name is unfortunate, as everyone seems to *assume* it must be some derivative cryptocurrency, when in fact it is an anonymity extension to Bitcoin.