There are relatively low volumes but steady price gains over the past month.
This could be a sign that a lot of people want to get into the market quickly without reasoning about the price. When we look in the order book of one of the larger exchanges (mtgox) we see that there is not much market depth on either side[1].
This coincides with large volume peaks when articles are published, for example August 3 when bitcoin broke the $10.00 price this was widely published about (also on HN).