These categories aren't particularly accurate, sorry. I haven't been meticulously 'tagging' my articles over the years, so this is a naive automated categorisation, based on looking for related keywords. Given sufficient time I'd use a better classification algorithm. It's one of those topics that the academic world is really really into. Like if you ever have trouble sleeping, call your favorite NLP CompSci PhD and ask her if there's some way you can classify blog posts automatically.
I also haven't built one of those tag clouds that were so popular in 2005. Are we officially over those yet? Or are they retro and cool again? I can never remember.