Do you think a country should have an official language or emphasize the need for a common language?

This question grew from answers to this question.

In America we have no official language, but obviously English is the common language spoken. Some argue for legally making English the official language, some like it how it is without an official language.

I think having a common language in a country is important. I don’t have a strong opinion on making it the official language, not yet at least, I look forward to reading everyone’s answers. I am very understanding when new immigrants come here, and the struggle they might have learning the language, especially older adults. What is important to me is the children raised and born here learn proper English in our schools, which is basically how it is set up. I am all for publishing instructions and documents in multiple languages. I am completely fine with things like tests for drivers licenses being offered in foreign languages. A common language allows for people to have the opportunities offered in the whole country. Anyone who does not speak English in America is more limited to where they can work, and where they will feel most comfortable living.

Let us know how it is in your country and what your opinions are on the topic.