And Information Darkness Descends on the LandNPD announced this week that they will longer be publicly distributing monthly hardware sales data. Also, they made some changes in how software sales are reported to draw the veil over those numbers as well. See the gory details here.
If you'll remember, they tried this back in 2007, then withdrew less than a week later in response to public criticism. Interestingly, though, no one really seems to care this time.
NPD did note that their subscribers are allowed to release sales for their own products if they wish, so we may still be getting partial information. It's highly likely, though, that this is being done in response to pushback from publishers and hardware companies. It is, after all, free monthly publicity for NPD, so they really have no good reason to stop of their own accord.