Why do people blog?  Is it for fame or fortune?  I think it must be principally for fame since most people realize they will never realistically ever make any significant amount of money off of their blog (not unless they were famous). 

Fame is a very powerful motivator.  Our culture worships fame and there is probably a strong evolutionary biological component to the desire- and need- for fame in social groups.  Fame = social capital = social influence/power = security and control over resources like people's attention.  Fame, in many ways, defines leaders and provides a sense of social order which is necessary for social animals like us.  Heady stuff. 

Some people may object and say they create their blogs for purely personal, introspective reasons.  In some cases, I am sure they are correct, but I think most bloggers are extroverts and want the notoriety a blog can bring.  For the extroverts, if no one ever reads their blog, or comments on it, I think most will give up blogging.  They will have lost their sustaining motivation. 

This is potentially a big problem for entrepreneurs who hope to profit from the coming early majority blogger adoption boom. 

As millions more bloggers come online, the challenge of garnering significant amounts of people's attention (which converts to social capital and, therefore, personal fame) is going to grow exponentially more difficult.  Fame, as measured by services like Google, Popdex, Technorati, etc, is going to grow very far out of reach for nearly all bloggers.  This will be very frustrating for many people unless expectations get reset. 

So the question becomes, how does blogosphere success get redefined to make sure blogs become a permanent part of the mainstream and are not some digital equivalent of an algae bloom where the population explodes, chokes off the resources it needs to survive, and then dies. 

For blogs to really change the world, everyone needs one, but the current infrastructure in which success is defined by global rankings is not sustainable for the vast majority in a blog-saturated world. 

For the average blogger, fame-as-success model needs to become pride in publishing on what is effectively the new refrigerator door.  It needs to move away from being stack-ranked against bOING bOING and become much, much more socially localized.  We need to encourage the concept of micro-fame among one's peers, friends, and families.  This is both a technical infrastructure change and a social redefinition. 

I am not sure how to best do that but I think that if we look at things like photography, we can see how it evolved from a very specialized and insular community of Photographers into a mass-market of snap-shot takers.  Will blogs do to publishing fame what the Kodak Moment did to photography?

I don't know.  Perhaps they already have.