They're just counting views in a particularly unrealistic but technically not incorrect way. Seems to be pretty much par for the course, like when twitter announces a billion new users, most of which are probably bots and/or quora.
If Posterous can't provide meaningful stats (and I appreciate that filtering out bots may be non-trivial) then they should just avoid providing stats altogether. Bad data is worse than no data as it's much more misleading.