Until Apple is more forthcoming and the security community has done deep analysis on Passbook, it's probably best to use it only for things that you don't consider real money. I'll be testing it that way. And I would strongly suggest that you steer clear of Passbook if you aren't going to use a strong passcode on your device.

There's another hidden consumer security issue in iOS 6. Prior to this release, your apps had access to your device's Unique Device IDentifier (UDID). They can, and frequently did, use the UDID to track users and sessions, as well as to collect marketing data about your usage. Apple wisely deprecated access to UDIDs recently, and they're now completely inaccessible to apps via the review process in the Apple App Store.

That's all to the good, but UDIDs have been replaced by a thing internally called "identifierForVendor." This identifier, which is unique per vendor, can be used similarly to UDIDs for tracking your activities, sessions, etc.

How is that an improvement? For one thing, each vendor identifier gets wiped when the device is wiped, so if you decide to sell your device, the new user won't get your same ID.

The nice part for consumers: You have the ability to restrict access to vendor identifiers. (Go to Settings --> General --> About --> Advertising and turn ON the "Limit Ad Tracking" toggle.)