There are several factual inaccuracies in his post and unreasonable assumptions.
1) I believe that Flickr sold for $17 + a small earn out. The only authentic data on this is a post by Rafat on paidcontent.org.
2) You can't get at potential freemium subscribers by total uniques! Most Flickr viewers are not Flickr members! You need the actual uploader count and then at the very very best 1% might pay.
3) The ecommerce number is probably significantly off (2-3x) because Flickr is all about online sharing.
4) Flickr is huge but unfortunately is losing community aspects to other channels now like Facebook and twitter.
5) For another comparable, Webshots sold late last year for $45M and was probably 3x revenue.
Ultimately, Flickr has a pristine brand, leads the photo sharing category, so I'd guess it deserves a premium above photobucket so if Yahoo decided to sell then maybe $300-350M.
The bottom line is that there will never be big money in photos.