Yeah well you know what your getting yourself into when you JB. When you jailbreak your device your are actually removing some of apples security checks and allowing any app to do whatever it wants (even app store apps that have been through the review process can be of some danger after JB).
This is very informative. What would the apps do? Inquiring Minds Wanna Know.
Key log, forward information from your hard drive to remote servers, remote access your computer, record your usernames and passwords when you log into bank/credit accounts, send your address and phone number to all members of ipaddorums . . Anything and everything