In follow up to DG one thing to point out is that bid sitting low floaters that are trading well below there 20 day MA of volume on a day to day basis can negatively impact the stock.
The seller at the ask has a certain amount of shares to sell and until, or unless, those shares are bought the stock will not move up. If they sit there long enough without getting filled, there is a good chance this seller will lower his sell order price thus lowering the ask.
If folks bid sit, the MM's see all those orders sitting there and will move their ask down to fill them if there is not alot of action on the ask (stupid level 3 lol).
As we briefly saw yesterday in BFHJ, in a low float if a few people start selling on the bid, it starts to cause panic in other shareholders as they see the bid / ask start to drop, so they start bid whacking as well, and we all know what happens then.