Everyone has their coping mechanisms. I don't think there is anything wrong with imaginary friends, as long as they don't interfere with your life. Like said above, if it bothers you then seek help but if not then i don't see anything wrong with it. You would be surprised at how abnormal normal people really are. ;)
It sounds odd. You don't acknowledge these imaginary friends around others do you? What you do alone is your business. At least we jmo you're not SZ. Cause after talking to yourself for so long.. hey do your imaginary friends have different personalities?