So Groupon filed its S1. The length of the document and the analysis of it is staggering. So this is a blog. A web log. Here are some of my favorite reads on Groupon's filing.

Who Will Be Left Standing Post-Groupon IPO by Erika Morphy of Forbes. An analysis of the daily deal market. Not sure if I agree with her assessment of AT&T, never really seen them as sophisticated at marketing in unregulated markets.

Groupon S-1: Mind The Ratios. A nice article by Jeff Bussgang of Flybridge Capital about deteriorating customer and merchant growth ratios. Those Boston VCs like to pound the numbers.

"Anyone can start a Groupon!" and other startup myths by Andrew Chen lays out some barriers to scale.

Andrew's post led me to Groupon S-1 Reveals Business Model Deteriorating in Oldest Markets by David Sinsky of Yipit.

Sorry, There's Just No Good Excuse For The Amount Of Insider Selling Going On At Groupon by Pascal-Emmanuael Gobry. The title says all that needs to be said.

Groupon IPO: pass on this deal by David Heinemeir Hansson a partner at 37Signals (whose founder Jason Fried sat on the Groupon board for a few years) has a blistering attack on the use of Adjusted Consolidated Segment Operating Income or ACSOI as an accounting metric. Groupon without marketing expenses is not Groupon at all. Indeed.

3 Reasons To Feel Good About Groupon's IPO from the Wall Street Journal. Hugely profitable, scale, and losing money for a while is all good.

My bottom line. Groupon is the leader in a huge market and its growth has been astonishing. They are going to go public and cash a lot of people out. They made the market and are going to be a market leader for some time. A $20 billion valuation seems a bit rich.