why companies still push out proprietary connecters is beyond me.. steve jobs is still laughing at us from the beyond, thank god for natural botanical cancer treatments...... to soon? .... i digress.
Not to sound like a SteelJan fanboi, but she has a really good point in one of her instructional vids about connectors. Just because you CAN connect any 510 threadded Atty/Carto to any 510 threadded battery doesn't mean you should. Obviously each person should do some research to see if their devices are "compatible" so you don't end up discharging your battery in the danger zone.
I think proprietary connectors are good, but only as far as voltage / wattage throughput is concerned. Low voltage should have one standard. Med voltage should have a second, and high voltage should have a third. You shouldn't ever be able to connect two devices that have the potential to lead to catestrophic failure, which is completely possible with the current 510 standard. Also the use of USB as the standard charging connection should only be used if you can safely charge via a computer's USB port. Some devices that use a USB charging solution will draw enough current do seriously damage your circuit board. Unfortunately the general public just sees a USB Plug, and a USB receptical and assumes the two are compatible.
As to the Apple connector thing, just about every IT manufacturer uses this method. Not only do they generate revenue from the device they've made, but they also generate revenue from anyone who uses their connector in their accessories. At least Apple standardized the iPod connector on all of their portable devices (iPod/iPhone/iPad) instead of making you use a different one for each. That would have sucked.