What's interesting to note is you'll see say 50k or 100k on the bid, and then a 200k sell prints. Doesn't move the bid, until much more selling comes.
I see this as 1 of 2 things, and both are good.
1) MMs are swapping shares to induce selling to increase their own holding or cover short positions.
2) There is a big buyer in our midst who is picking up shares quietly. I also tend to believe it's this because we've seen all a long large buyers at almost any price. Someone is accumulating, trying to lock up that float. I wouldn't be surprised if it was someone related to the company, or a big fund.