Last week Mike Arrington wrote a post on Facebook turning down an offer to invest at a $2bn valuation. I left a comment on that post saying that I thought that $2bn price was low given the prices being paid in the Facebook secondary market. Later that day, I got a private email with a price chart for Facebook common since January 2008. I was asked not to publish that chart so I won’t. That chart showed that Facebook common has traded as low as $6/share earlier this year but is now trading around $8/share. That translates into $3bn to $3.5bn, lower than I had suggested in my Techcrunch comment.