There is also the inverse problem on some input interfaces. I do have to write emails, sms, weibos, HN comments in English, Chinese and French. I don't know how ios handle this issue but on you have to open a thing, tap, close, and it is not very convenient. I use Swype beta, which is actually good, but it is annoying to live in a world where monolingual is the norm.

I have no figure but I'd guess multilingual is actually the norm in many countries.