Car chargers for usb devices

I purchased a 12-volt USB charger.  It seems to work ok with iPhone and iPod touch.  But it didn't work with Blackberry phone. What's up?  Isn't USB the same?

USB 2.0 - states 100mA to 500mA - when it is used to transmit data.  The same up to 500mA USB bus port (notebook, desktop) charges iPhone OK, it also charges iPad and some other devices, but not all USB devices. Why?

The standard iPhone USB AC Power "brick"  says
100-240V 50/60Hz 5V 1 A.

The iPad AC power block says
100-240V 50/60Hz 5.1V 2.1A

The Blackberry "power plug" says

100-240V 200mAh 50-60HZ 11-17 VA - Output: 5V-750mAh