Re: bluetooth
One "problem" with this system is that it was originally intended to replace cables between computers and peripherals. The cost has not dropped to the predicted low level and so it is not cost competitive with cables.
The other problem is the protocol which only allows a closed network. The market for short range wireless connectivity wants roaming nodes to be able to get into the closest network.
Another problem is the "crashing" of networks which consumers will not accept. No one wants to be a computer expert and reboot systems just to make their wireless headsets play music from their hi fi sets.