Android no le da formato automático a la SD card (al menos no en el Samsung Galaxy S y S II) pero, al mismo tiempo, no acepta cualquier cosa, por ej: no puedo poner mi música en pictures\pepito (al menos a mi no me funcionó).

Buscando en los foros encontré esto:

• Music/ – Media scanner classifies all media found here as user music.
• Podcasts/ – Media scanner classifies all media found here as a podcast.
• Ringtones/ – Media scanner classifies all media found here as a ringtone.
• Alarms/ – Media scanner classifies all media found here as an alarm sound.
• Notifications/ – Media scanner classifies all media found here as a notification sound.
• Pictures/ – All photos (excluding those taken with the camera).
• Movies/ – All movies (excluding those taken with the camcorder).
• Download/ – Miscellaneous downloads.

Esto lo saqué de aquí:

http://developer.android.com/guide/topics/data/data-storage.html#filesExternal

J