Guessing Model S sales with any sort of accuracy is difficult, if not impossible, because Tesla, unlike other automakers, doesn't publish monthly sales figures (it only does so quarterly). Additionally, the California-based company lumps its global sales into one quarterly total. That means domestic Model S sales aren't disclosed either. So, when Tesla publishes its 2014 sales figures later this month, that's all the public will know: the 2014 global sales of the Model S. No more, no less.
Daily Kanban went on its rant largely because some publications sounded an alarm of sorts by saying Model S sales plunged between December and January. The site also compared estimates by Autodata, Automotive News and Inside EVs with actual US registrations (as captured by Polk Automotive) and basically uncovered a lot of spitting into the wind.
For the record, we stopped calculating Model S estimates in our green-car monthly sales estimates because of such lack of transparency. Here's hoping that Tesla eventually starts making its US sales figures public, but until then (and we'll likely be waiting a long time), it's anyone's guess.