"And why do you throw rice at the bride and groom? The custom originated with the ancient Assyrians, Hebrews, and Egyptians as a symbol of fertility and good wishes for a bountiful life. Although nowadays, you’re more likely to throw confetti, flower petals or the ever-popular bubbles. That tradition began due to the fact that rice is bad for birds to eat. " source: http://www.buzzle.com/articles/why-we-t ... ealed.html
p.s.1: very good article in the link above. p.s.2: I'd prefer flower petals instead of rice.