Short answer: To exercise my english.
Not-so-long answer: As the majority of the people who starts a blog, I don't really expect to have much readers. So, I found another reason to blog: learning to express some ideas in a language that I don't master. I'm very good at reading english, as it is a very needed skill if you are a programmer. But at writing, I'm not so good. I'm forced to spend too much time on every english text I write, and think that's just matter of practice.
So, if you (the imaginary reader) find any error on my writings, please correct me.
I also have to admit that I'm bad at speaking and listening english. I'm watching english movies with english subtitles to fix the later, but don't know how to improve the former.