What language is your internet?

I blog in English here, but I also maintain a French/Japanese blog within a language learning community. I tweet in English and German (and keep a separate Klingon Twitter account, though I haven't updated it in a while). I've edited German, English and Klingon wikis. I've been an active member in English and German forums. I write instant messages in more languages than I actually speak.
Online, you can be any language you like. How do we chose which one we are going to use?
Some of my choices were made in specific biographical contexts. I started this blog as part of an Open University course. People from a wide variety of language backgrounds were studying on that course, but all shared English as one of their languages. Choosing English meant choosing to communicate (potentially) with all of them. Still, I've finished my studies at the OU and here I am, still blogging away in English, though many, if not most of my readers are native speakers of German.
Sometimes, I have chosen a language specifically to improve my skills in that language. The exercise factor explains most of my activities in French, Japanese and Klingon (OK, the geek factor may also play into this, especially in the case of good-ol' tlhIngan Hol). Of course I am also able to reach a different audience when blogging in Japanese than when blogging in English, but with fairly rudimentary language skills that neither allow me to really build relationships with readers or to express ideas worth expressing, I am not sure how important this is for my choice of language. Writing for an abstract Japanese micro-audience is different from writing for an audience of English-using fellow students that I already know.
In some cases, my choice of language has also followed from the need to get specific information. While there is no lack of German online forums, the more specific your interests get, the bigger the chance to find something in English. There may be two or three German forums to choose from, but dozens of English ones available, each with their own focus, culture, traditions, and often with a larger number of contributors or active threads. I won't deny, though, that the sheer fun of writing in English and experimenting with different language roles also plays into this.

So: What languages do you use online, and why?