Call me a pragmatist if you want, but I think this is the most important point in choosing a language. No matter how beautiful, exotic and original your language is, you need to practice it. Many languages offer a lot of speakers (like chinese if you live in San Fransisco), great travels (spanish for Americans), a wonderful littlerature and newspapers (like russian) or are just plain useful (think of english). But if you learn farsi (persian, the language of Iran) you'll have a hard time finding someone to talk to unless you marry an Iranian, travelling is not the easiest thing you can imagine and litterature is rather limited. So why work so much just to tell people at parties that you learned such-an-exotic-language if that's all you can do with it? You will forget it quickly if you can't practice it.

On the other side of the same coin, knowing a useful language allows you to practice it everyday and to open many friendship, career and business opportunities. Of course, usefulness depends on your life and the country you live in. I took italian because Italy is beautiful and just next door, and I had some business to do there. Actually, I could do business in other languages but it really is not the same. And italian is one of the most beautiful languages there is, with plenty of incredible opera airs to sing while bathing.

So my advice is : if you want to learn an exotic language for the sake of it, think twice.