In my view, yes, incorporation is almost always a good idea.
I don't think I could say it better than this link:
http://sbinfocanada.about.com/cs/sta...orporatadv.htm
If your business is smaller than say, $50K in revenue per year and you don't have a lot of supplier purchases, I might say don't bother.
Remember on an annual basis it will cost you money to keep the company active.