Hi Alphonso,
I hadn't figured it out - and it was an annoyance for me since moving up to WM5. The ability so send Contacts via Bluetooth to my Mobile Phone (a Sony Ericsson k600i) has been much missed since moving from Windows Mobile 2003SE.
Unfortunately, in my case, sending a Contact via BT manages to crash my 'phone!
The BT connection is made (the BT icons shows up on my phone), the contact starts to send... but then the Mobile Phone screen dims, and finally reboots.
Sending Contacts from a Bluetooth enabled PC to my 'phone works just fine though... so the problem appears to lie with the PDA.
If anyone else has found this, or a workaround, I'd be interested to hear it!