I would say the difference between The DAO and everything that has gone before is that The DAO doesn't have a defined objective other than to fund other projects. Ethereum, BitShares, Mastercoin, and even Slock.it all have relatively defined purpose and the people buying into those projects are making individual investment decisions.

The DAO is the first DAO that expects people to give up their individual control in favor of community control. In the spirit of protecting individual control The DAO allows splitting. This splitting and/or selling out of The DAO will be the preferred method.

After all, given 3 projects that get funded by The DAO, chances are you only care about/believe in 1 of them. But by participating inThe DAO you get exposed to all three. By not participating in The DAO you can focus your investment dollars on the projects you most believe in.