Originally Posted by tsac
My thought is the charging cable may allow the BB to detect the connection to the USB port by seeing the data pins. The RIM charger may have either a loop or other way of telling the BB its connected and therefore allow the BB to charge. I would suspect aftermarket chargers may not be able to do this.
Only my thought.
I included the document on charging characteristics KB18223-Charging behavior of the BlackBerry smartphone
This was definitely the case with Nokia devices in their original Micro USB chargers as well as their old headsets.