It has been ages since Amazon updated their BlackBerry Kindle App. The latest update brings them to version 18.104.22.168 from the previous 22.214.171.124. Not a huge version jump but they have not done an update since it was released. My guess is the new version adds support for more BlackBerry devices and fixes bugs but who knows.
You can pick up the updated Amazon Kindle app for BlackBerry at www.amazon.com/bb. Keep in mind it is still limited to US customers only which sucks.
Thanks Nikolaus for the tip!