Apps get approved, but "trustworthy" is kind of vague... They probably check for malware, but stuff like poorly written, bogs down the system, or doesn't do what it's supposed to, things like that they can't really check for...
RIM, like every other company on the planet now, takes the 'hands-off' approach. The people held responsible are of course, never the consumer, and never the company, which leaves the developer.
So if you have any problems, it'll be some college kid getting nailed to the wall for it, not RIM.