The source of the big delay in getting DayZ out was because of the new architecture that we built. As part of this, we spent a great deal of time making very efficient and new ways of doing things. Many of the problems of ArmA for security were by design, doors used by the application to achieve its needs. In ArmA these could not be closed, in DayZ we no longer need them. We thought we had closed some of them, but we found one and we've fixed it. However because some people will have spawned items, we decided to wipe the database to provide a clean slate.
All existing characters have been killed, if you are currently logged in when you next join your character will be dead.
This is all part of the testing process, we've identified some additional areas of security and enabled some we had left off so we could really see the holes in the architecture without having to rely on the higher tier security measures. Because the vulnerability would allow a player to create items (and they had been) we have decided to wipe the whole database. We could not announce this, as we didn't want to encourage those exploiting to try and figure out a way of leaving items on the ground. We have killed all characters in the database, who existed after all our servers moved to the new version (0.29).
Please Note: It is more than likely that we will, much like other software, be continually identifying and patching these kinds of critical security vulnerabilities.
Important updates like this WILL attract database wipes during the alpha process. We apologize for the inconvenience but I am sure everyone can agree, it is not fair to keep going with the bad data and some of the unfinished items were spawned in game - which could cause crashes and other issues thus confusing our alpha testing. Many people were experiencing crashes relating to these items that had been created in the game.
I realize this is a little vague, but its our policy to be suitably vague about specifics regarding implemented security measures.