Just How Secure is BlackBerry OS under a BIS?

[CybaCowboy]

Wirelessly posted (RIM BlackBerry Curve 8300: BlackBerry8300/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/122)

Okay,

We all know that BlackBerry OS is ridiciously secure when used with a BlackBerry Enterprise Solution (BES) - this is the reason the operating system has been so popular with enterprise and Government customers for so long - but what about for BlackBerry Individual Solution (BIS) customers?

Really, just how secure is BlackBerry OS?

Have there ever been any known security issues (in ANY form)?

What is the possibility of someone secretly accessing your device's information (ala. Paris Hilton's SideKick/HipTop)?

By the way, viruses don't count - with only one or two minor exceptions, the only viruses for mobile devices that have existed have been "proof-of-concept" viruses, and none of these have knowingly made it "into the wild"...