Forester says that in 2008 2/3 of laptops shipped with Bluetooth capability built-in and it's still rising fast. 100% of Macs and smartphones have it. USB adapters are regularly less than $15.
There are lots of things wrong with bluetooth but availability is not one of them!
Personally, I just replaced my USB headphones with over-ear bluetooth headphones and, although their audio quality is lacking, I'd hate to go back. May I go the rest of my life without needing to untangle the cord from my office chair again, or forgetting that the headphones are around my neck as I walk away.
Now, why do all bluetooth headphones and headsets have that awful 1-button interface?? Press for 2 seconds to turn on, 3 seconds to turn off, 4 seconds to pair, 5 seconds to display battery, etc. It's idiotic! I hope this gets fixed soon.