Does a jailbreak loose any data?

[FredZ]

I'm getting ready to jailbreak so that I can use slingplayer over 3G. I'm curious what will happen if I jailbreak: will I lose my app store apps, contacts, emails, music, or other app specific data?

 

[jamesus]

Technically you shouldn't, but having a backup or all of your data outside of iTunes is a good idea. Apps, music, and anything else contained in iTunes will sync if you have problems and need to restore. As for contacts, I'd use a trial of Mobile Me to backup the contacts. Emails should just sync back once you re-enter the account information.