Nor should you want to.
I am constantly amazed how willing people are to install software on their bb's without a clue of what it might be doing.
For example, how many times do you see an offer for a "free trial of application x"? Dozens of people jump on it and install it.
Now what if that software were really reflecting your emails to a third party? What if they employ keystroke logging and forwarding? What if they are really just SPAM engines?
Even something as trivial as a spell checker is sending the contents of your messages to a third party server. You may trust Google, or netenza, but that's your choice. (and yes, I have removed the spell checker I got working yesterday as a test).
None of these issues have bitten this community yet. And I say "yet" with a hunch that it won't be "ever".
The information on our bb's is extremely valuable to us. Considering some of the people you see carrying them - from military to political to cxo's - I'm sure it is extremely valuable to someone else. It won't take a lot of skill to read it.
Just a thought from a security perspective.