Not everyone scans cards. Most of these are only issues for people like that author that scan business cards and then destroy them. That said, it's important to have a blank back you can write on if you need to.
In non-Roman-alphabet countries, it's quite common to have two-sided business cards with English on one side and the local language on the other.
Re: Common business card mistakes
#21Which is terrible. If you really need business cards in two languages, just order two different sets.