Jailbreak and iOS 'hardware encrypted' data My understanding of reading apple security document below
http://images.apple.com/ipad/business/pdf/iPad_Security_Overview.pdf

is that using iphone4s or ipad3, 

and setting a complex passcode, 

the data on the iPhone/ipad is encrypted when iphone/ipad is locked.

If iPhone/ipad is jailbroken, does it mean the original data is lost ?
There are two partitions on all iOS devices. One is for the system, other is for the data. Jailbreaking only affects the System partition. So jailbreaking doesn’t affect your data.