I had not heard of Instinet before, and this is what their Wiki page says about them:

Instinet is an institutional, agency-only broker that also serves as the independent equity trading arm of its parent, Nomura Group. It executes trades for asset management firms,hedge funds, insurance companies, mutual funds and pension funds.

This doesn't look to me like their trading is being done by or for average joe's like most of us. In fact, it points to the fact that there is very likely some insitutional money in POET already. Hedge fund perhaps? If that is true, could yesterday's selling have been a "shot across the bow" of the good ship POET to live up to the timelines they set out? A "Here's what us selling a mere fraction of our shares can do to your share price, so get on with it" type of message?