iFuntastic has grown into a quite powerful program.
Like all powerful tools, it must be used responsibly.
Some of the operations it enables you to do may be illegal where you live.
Please inform yourself and think, before you do something that may get you into trouble!
iFuntastic will copy files to your phone, modify the phone's system and other files, and generally root around in its innards.
While this usually works, there are no guarantees. Use at your own risk (it can't be stressed enough.)
Future iPhone Software Updates may break iFuntastic inadvertently or purposefully.
Depending on the details, there may be nothing that can be done about it.
Be careful with third party applications. They execute code on your phone and may do all sorts of intentional and untintentional damage.
(Much like iFuntastic - but any (unknown) damage it may be doing is at least unintentional.)
No matter what happens, a 'Restore' of your phone should always get it back into a pristine, if slightly boring, condition.