I have been using my SSAN for 8 years..as sole proprietor...and as for protecting your designs...I for one don't worry about it...if someone takes my design, it will cost me 30-50 as a minimum to take legal action which may or maynot be successful...and then there are different jurisdictions to worry about and the likely hood of my stuff being a house hold name is not to high...If I were you, I would just worry about getting some designs out and make some money first