From a practical point of view, you are better off having bigger lists as it's easier to build momentum that way. Smaller lists have a harder time reaching a certain critical mass and getting things accomplished, while people feel much better about posting on a list where there's lots happening already.
I agree with this.I don't see that it's a problem for us to have the odd comment or post in a language other than English. It seems to me to be less friendly to suggest that people *must* write in a language that they don't necessarily speak well. However I guess having a list that works that way would mean people like me, who only speak one language (yes I know that's pathetic, but there you go) might have to ask for a translation at times, so we can know what's going on. I wouldn't mind that at all, as long as there are people about who wouldn't mind translating things occasionally, if they can.