What do you call the symbol on the left? And do you ever use it? I’d say “pound” and I type it fairly regularly when doing scripting for websites I work on — most commonly to introduce a comment in the script. But it’s got lots of other names: hash, octothorpe, hex and even more uses (see here on wikipedia).
Why am I thinking about the octothorpe? As I notice more and more twitter feeds on the blogs I read, I wonder why the twitter folks picked # to preface tags. I went off to figure it out, and found a nice typography blog on British newspaper, the Guardian, website. They recently ran a post on the rise of the usage of the octothorpe. Check out all the posts here.