The problem is twofold. You mention the one where those with designs will get others to collude with them to use force to get the fruits of your sweat. The other part of that problem is all the spineless people who don't understand the power these evil goons get is due to their acquiescence. If at this moment everyone said fiat was worthless and flushed it down their toilet it would be worthless. But people seem to need their experts.
It will shape up just like everything else, those who brave the frontier will watch the farmers of men come behind them using their sheeple as a shield as they seek to take over ownership.
There are always going to be bad coins that people get tricked into using. Fedcoins will pop up like wildfire and attract the followers gullible enough to use them.
I'm extremely not worried about this outcome though. It's the good coins you have to look at. Can they rise up and show that a cooperative economy is superior to a competitive one? If not, it was all just hype to begin with.