If you use USD and want Yen you don't necessarily have to exchange them. You can start working for Yen. It's the same with bitcoins. You don't have to buy them you can just start services to earn them. I like it better because then you don't have to give out your ID to some online company!
That's an extremely limited niche, though. It's like selling stuff for bitcoin--your market is very small. It's better to earn fiat and buy bitcoin. And fiat is more stable. Would you really want your paycheck in bitcoin?
Actually there is now an option to get your paycheck paid in bitcoin! And you don't even really need to get your employer to agree to do so.
You could look up bitwage to see what I am talking about. Apparently you can even set a percentage of your paycheck to be paid to your bitwallet.
I am looking forward to try it out myself once i get proper employment. Beats having to buy it and worry about whether you're getting it or not.