I've wondered about this. However, I keep comming back to the following:
Why would you exclude a language. If no one visits needing it, then it is not an issue. If someone does visit that is more comfortable in that language, then why not let him see it?
I know that maybe the site data is not in most languages. But then the visitor is no worse for those than without the Zenphoto languages present. In fact, he is better, because at least some standard text is translated.