Multitasking vs. focusing on a single task is always a delicate balance.

Push too far towards the multitasking and you get people with severe ADD.

Push too far towards singular focus and you get autism.

It is a delicate balance not to go too far in either direction, although there are times when a singular focus is actually highly useful (i.e. a surgeon during a complex procedure). I am of the opinion that the ability to handle multiple tasks with a minimum of loss of efficiency is as variable as other personal traits (intelligence, creativity, etc.) although with training I think that anyone can become more proficient at handling multiple tasks.