Just in case there was any doubt about Posterous not filtering out bots given that Garry hasn't specifically admitted it:
http://twitter.com/#!/richiepear/status/13809170130149376
Rich Pearson (VP Marketing - Posterous)
@imranghory No - we just don't filter out your own views
and search engine visits
If the majority of page views are generates by bots then the number of page views you show isn't even a ballpark figure indicating how interesting/visited the blog post is. It's simply a semi-random number depending on crawlers/bot activity and nothing to do with real human visitors.
If you were simply off by 10% I could accept your answer, but you seem to be regularly off by a factor 200-300%.