I'd like to address the question of whether it makes a difference if someone announces that they are going to be buying (or selling) a large amount. Probably not, if you do it over time. You could probably easily pick up half a million a day without driving the price too high. The market makers like stable prices- they make money on the spread, but may lose money trying to keep the market "liquid" if the price is moving too rapidly in either direction. So if you have multiple daily buys spread out over a week or two, you could probably build up a sizable chunk without driving the price. With volumes varying from ~1-4 million, another 1/2M a day wouldn't raise too many eyebrows.

Of course, if a number of people or groups are trying to get in at the same time, no telling what will happen... Especially if there is news.