1) Momentum. Ethereum is (by many measures) the top performing alt coin. It's the most likely to be accepted on random websites, companies are investing in it and it looks like it has interesting potential. People see that and jump on, hoping the momentum will continue.
2) Stability. Crypto-nerds like you and me look at DAO and shake our heads, "reverting transactions goes against the whole concept". But to investors it looks like stability, which is attractive to them. There is now the implication that the developers will step in and fix any major mistakes. It's not just ill-defined smart contracts, theoretically the developers could intervene in cases of stolen ETH from wallets of major exchanges, or anything really which could threaten the stability of the currency as a whole.