Hopefully you really have a good answer for this. Getting hacked is no longer a distant probability; it's a harsh reality. The most recent incident was Evernote losing customer information including email addresses and passwords to a hacker. I'm an Evernote customer and I watched the drama unfold from the perspective of an end user. I have no visibility into what level of security response planning Evernote had in place but this is what I would encourage all the critical services to have:
You are as secured as your weakest link; do anything and everything that you can to prevent such incidents. This includes hardening your systems, educating employees on social engineering, and enforce security policies. Broadly speaking there are two kinds of incidents - hijacking of a specific account(s) and getting unauthorizd access to a large set of data. Both of these could be devastating and they both need to prevented differently. In the case of Evernote they did turn on two-factor authentication but it doesn't solve the problem of data being stolen from their systems. Google has done an outstanding job hardening their security to prevent account hijacking. Explore shared-secret options where partial data loss doesn't lead to compromised accounts.
If you do get hacked, is your system instrumented to respond to such an incident? It includes locking acconts down, taking critical systems offline, assess the extent of damage etc. In the case of Evernote I found out about the breach from Twitter long before Evernote sent me an email asking to change the password. This approach has a major flaw: if someone already had my password (hard to decrypt a salted and hashed value but still) they could have logged in and changed the password and would have had full access to my account. And, this move—logging in and changing the password—wouldn't have raised any alarms on the Evernote side since that's exactly what they would expect users to do. A pretty weak approach. A slightly better way would have been to ask users to reset the password and then follow up with an email verification process before users could access the account.
If the accounts did get hacked and the hackers did get control over certain accounts and got access to certain sensitive information what would you do? Turns out the companies don't have a good answer or any answer for this. They just wish such things won't happen to them. But, that's no longer true. There have been horror stories on people losing access to their Google accounts. Such accounts are further used for malicious activities such as sending out emails to all contacts asking to wire you money due to you being robbed in
Photo courtesy: Daniele Margaroli