Many reasons for leasing, although I bought my M5 sticker-cash with $1000 down in 1998.
Business write off is my main reason to lease a car (gonna be 2001 M Roadster, $1000 down again). I can completely write off my monthly lease from my gross income as a business expense thus virtually tax free money spent. Whereas to buy a car, you will have to write it off with depreciation and interest expense (if you're financing).
Not sure about State law, but I think it is better off leasing than financing/buying in Ontario.
For a car that you don't intend to keep for long, leasing is the best way to go. On the flip side however, if you change your mind faster than your lease expires, then you are in trouble.
But as I say, I bought my M5, and that goes to show how much I applause the beast