No, although you do need a margin account to short you have only borrowed the stock against your account. When you cover the ( margin loan for borrowed shares) by purchasing open market shares the borrowed shares are taken out of escrow and returned to the brokers treasury; you now own the covered shares you purchased in the open market. Now, naked air shares are never borrowed and don't actually exist, this is illegal and many usually get caught.
This is a very good synopsis of naked shorting in the big indices. The same occurs in pinks but is probably 200 times less likely to be examined by Finra/SEC regulators since they are unable to regulate naked shorting and FTDs on the big boards. CDs exacerbate the problem via volume but also allow the naked shorts to cover. IMO, this can be seen in the PVSP chart. http://www.bloomberg.com/apps/news?pid=newsarchive&sid=aEOpTqmLZB7A
News 
Market Data 
Discover 
AI
