In the wake of Microsoft’s aborted courtship of Yahoo and Jerry “Oh, did you increase your offer?” Yang, there’s bound to be a lot of scrutiny about what’s next for Yahoo.

One asset that’s well known but perhaps not scrutinized from an investment perspective is Flickr, the world’s most popular photo-sharing site that Yahoo picked up for a song (estimated $40 million) in 2005. Today, Flickr attracts more than 44 million unique visitors a month, according to Comscore, while Compete.com reports Flickr had 30 million unique visitors and 70.2 million page views in the U.S. last month.

Despite Flickr’s popularity, it is arguably under-monetized. In terms of advertising, it’s minimal at best. Instead, Flickr makes most of its money by selling Flickr Pro memberships for $24.95/year and offers e-commerce services through partners such as photocards, posters, frames and calendars.

So, what’s Flickr worth, and, more important, what could it be worth if it was managed more aggressively?

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