This is the first time I ever heard of it, I guess it is more American than European (or possibly connected to English/American language in some weird way). Were I to receive a document with double spaces I would have been very surprised, now at least I know that is just different things being taught rather than not knowing the proper way.
I was always taught to NEVER use more than one space after a period, starting on a typewriter and later on computers. To me double spaces would look like you are trying to make some odd statement, like using multiple exclamation marks with a one thrown in, or a similar oddity.
In a Swedish newspaper today the autopsy report of a bird said it a suffered blunt trauma (been hit by a truck, according to the truckdriver who said he had run over/through the flock of birds) and died from internal bleeding.
Thing is, there was/is a policy in place saying you are not allowed to hand out invitations at school unless you invite everyone, or all boys/girls separatley if you want all boy/girl party. If you want to invite only some people, you send the invitations in the mail. As usual, the parent did not check what applied, and decided to blame someone else for his mistake...
I was always taught to NEVER use more than one space after a period, starting on a typewriter and later on computers. To me double spaces would look like you are trying to make some odd statement, like using multiple exclamation marks with a one thrown in, or a similar oddity.