Exorbitantly large amounts of funds in the hands of unknown individuals whose security/business conduct is also unknown can be a hindrance to a healthy currency, since one could fear that an amount too large for the market to handle would be dumped onto the market (voluntarily or not) in a short timeframe.
You're not being ironic are you? By this logic, every stock and small sovereign currency is threatened by individuals and institutions with more dollars and euros than the market cap of entire industries and small countries.
Some people shoot their toe sometimes but it has not hindered weapons sales.
Actually, what you stated is correct. Every stock and small sovereign (edited to spellcheck) currency is threatened by the largest holder of dollars - ie, the U.S. Treasury.
To learn why - watch this relatively current assessment:
http://www.businessinsider.com/howard-davidowitz-dollar-crisis-dow-6000