This is certainly a good question. The reasons to open a blog can be numerous and among the most different. 
Currently the blog seems to be one of the formulas of communication more used, also in business circle, where it is used as tool of interaction among client-operator, consumer-firm. All it takes is making online a turn to find the blog of Google, of Yahoo, of Technorati... there is really the embarrassment of the choice.

A blog  brings a halo of charm around itself (let's admit it!) which, in some cases, it can be also conclusive as tool of fidelity.  But it is not only this. I'm talking about the style of the contents and above all of the communication. 
The decision to open a blog can be dictated by the need to communicate, to compare, to share ideas, opinions, feelings.

In my case, all the aforesaid components are there but also the wish to succeed in involving my friends. Many of whom are then, unconsciously, the interlocutors of my daily working life. 

My goal is to make a tool available for all those people who feel necessary to share same interests. . I don't know whether I will be able to succeed in my intent or not.

A blog requires devotion and constancy.