Bluetooth was horribly implemented by most devices and use cases. 8 device limit (although, I've rarely seen anything that supports pairing with more than one), wasn't really usable as a data connection for iPhone since that required jumping through certifications hoops, many Android implementations were broken, and not much that has Bluetooth goes beyond audio.
It could have been cool, but broken software stacks meant that nothing but the most basic profiles worked reliably and making something interesting meant it wouldn't work in the field. This whole iBeacon thing being anything but trivial makes me shutter at the lack of creativity for Bluetooth devices in the last decade.
Maybe things will get better with 4.1.