I'm familiar with Austrians (sometimes even think myself belonging to them), consider their theory of subjective value brilliant (which started with Carl Menger). I know what you mean here, but, I'm afraid, this idea is not the only option in this case (and probably not the best one either). If that guy accumulated 90% of all coins he would be a central bank himself (remember, there is no other currency in circulation but Bitcoin). He wouldn't need to spend the coins, he could just issue "paper" BTCs, allegedly covered by real bitcoins. And then we have Gresham's law...
Why would people accept paper BTC? People accepted paper gold because they didn't want to lug around gold bars. Bitcoin has a weight of zero and is even easier to hide than paper bills.
I didn't mean anything like notes made from actual paper (hoped this would be self-evident like today's paper gold). Something more like present Visas or MasterCards
Indeed, people may try to avoid accepting paper BTCs as much as possible if their aim is to hoard bitcoins (see goldbugs as an egregious example), but they are not always in the position to choose (see Weimar Germany as another example). Also, if they can always redeem paper BTCs for true bitcoins at any time (or at least promised to) and paper BTCs provide as much convenience as true bitcoins, I see no reasons why these bitcoin derivatives couldn't be used for everyday activities
The majority of people wouldn't probably need some advanced features of Bitcoin such as anonymity and whatnot, so the paper bitcoins might actually be made more convenient as a means of exchange (having been deprived of such features)...