Pentax on Flickr
In my nearly 5 years on flickr I cant remember a Pentax camera topping 500 daily users. The volume of K-5 pictures is pretty amazing too. I have no doubt that the K-5 will pass the K20D by June or July. Given the 2 1/2 year head start and the continuing popularity of the K20, what the K-5 is doing is spectacular.
I also rabidly follow that chart (for no reason in particular). The K10D had well over 600 daily users in early/mid 2007 and was No.1 Pentax camera on that chart even a year after K20D was released, which in part explains why it has over twice as many images as any other camera in the top 5, and why it is clear third even when it is more than 5 years old. (K20D actually was a lukewarm seller compared to K10D).
With K-5ii and K-5iis just released, the old K-5 will drop further (it is droppnig now, and has been for 2 months). I cannot see K10D ever being topped on that list in terms of numbers of images.
Also - no Pentax Q or K-01 (yet) ... Flickr is perhaps a 'western' oriented site (I think not too many Japanese photographers use it) and so this might just prove how relatively unpopular those models have been in USA/Europe - at least until the very recent price drops.