> Very true, we don't need everything to be pegged to a single currency. Another development that will make moving between crypto-currencies more fluid will be decentralized exchanges.

That's not the point. The point is knowing that you won't lose money by trying out altcoins. With sidechains, at any point you can claim back your original bitcoins. You won't be left holding the bag as it happens all the time with separate blockchain altcoins.