I saw a very interesting blog from Brad Feld from Mobius Venture which is very interesting as it encapsulates his understanding of how he made a series of investments.    A snippet from his blog is posted here and the complete blog can be found at the link below.

"When I dug in and started trying to understand RSS and blogging in the spring of 2004, I identified eight segments that I believed existed: Content Management Systems (CMS), Aggregators (Readers), Tools, Hosting, Content, Search, Analytics, and Advertising.  I used this as the framework for both exploring the impact of RSS and identifying companies that I might be interested in investing in.  My framework has evolved in the past year, especially once I realized that my technical analogy for how RSS evolved was going to be similar (but not equivalent) to how SMTP evolved.  I was a very successful investor in email-related technologies (and continue to enjoy being an investor in two successful email-related companies – Return Path and Postini), but also learned some “interesting” lessons about how quickly the dynamics could change as I had a huge financial win at one point in the “email direct marketing segment” with a company called MessageMedia that ultimately got slaughtered (more on that some other day)."

http://www.feld.com/blog/archives/2005/04/im_hot_on_feedb.html