Market makers jump in and out based on buy/sell orders from others. If the ask is .05 and you put a buy in for 100 @ .05 it doesn't mean your going to get it if they have an all or nothing clause on it.
If I put a sell order on my KLGG shares for $25 you will see scottrades market maker come into the fray.
And yes they can manipulate and go short where needed but they will usually only do this on increased volume so they don't get caught with their shorts down. And it goes both ways, up and down