If somebody with a 100K portfolio decides to keep 20K in eur to 'hedge' against the falling dollar(like some experts like to recommend) he is speculating on the euro expecting a return of something like 10%(dollar loses ten percent) return if he is right. Yet he is probably with a even higher expectation of return on his trading(say 15-40%). I dont think it doesn't make any sense to hedge or diversify, just put it all in dollars and swallow any loss the dollar might have. If your worried of some kind of dollar crash then I dont think you should trade in dollars at all