Suppose several large biotech exchange traded funds (i.e. ETFs) take big positions in a stock. Then, they loan out quite a few of those shares to shorts for selling into the market. All is fine until the shorts get caught with a rising price. The ETFs collect margin interest from the shorts whether the price goes down or up. Well, let's say that the shorts come back to the ETFs in a rising market, and say, "Give us some relief, guys. After all, we have been paying you all of this margin interest for additional income". So, the ETFs give in, and start selling the underlying stock at a profit, to bring its price down. The shorts can then cover, and the ETFs have taken a nice profit, and retain their short client partners. Comments?