Blackberries Everywhere!

I was at an airport and I wanted to mate my Bluetooth headphones to my tablet.  I told the headphones to become visible and told my tablet to look for visible Bluetooth devices.  I was shocked to see about 8  Blackberries and 1 device that did not identify itself.  I was travelling on a Friday, so the airport was filled with business travelers.  That explains the number of Blackberries.  I noticed the guy sitting next to me was using a Blackberry, so that accounts for one of them.  That still doesn't explain why they were all visible, though.  Bluetooth devices are supposed to remain hidden until you want to mate them with another device.  It is considered a security risk to leave something visible all the time.  Do Blackberries default to being visible all the time?