I want it to be clear that I am not speaking on the behalf of the Ethereum Foundation. The point of this post is not to address the handling of the DAO fork, but to share why I believe the hard fork is the right choice.
Why we should reverse the DAO heist
The Ethereum community should reverse the DAO heist, and return the ether invested to the DAO token holders (and the extraBalance to the DAO token purchasers) in order to mitigate negative externalities of the DAO heist.
“an externality is the cost or benefit that affects a party who did not choose to incur that cost or benefit.” — Wikipedia
I am thinking, for example, about externalities arising from legal and regulatory precedents.
Why a hard fork is the only reasonable way to reverse the heist
The soft fork failed, and the counterattack is not very promising
A soft fork that censors DAO attackers was attempted, but it was discovered to have a fundamental DoS vulnerability before it was triggered.Without a soft fork, the counterattack effort is not at all guaranteed to succeed.
The complication of negotiation
Negotiating is the optimal solution, if it leads to nearly all of the funds being returned. A counterattack that potentially leads to the funds moving back and forth forever could let us negotiate for the return of only some of the funds. Without a fork, therefore, we are not in a good place to negotiate with the attacker. Given that the soft fork has failed, only the credible possibility of a hard fork can put us in a strong position.Negotiating with the attacker(s?) is complicated somewhat by multiple otherattacks, which possibly are conducted by different attackers. While at least some of them may be willing to negotiate, any negotiation that leads to the return of funds will take at a long time.