It’s hard to believe, but long before rice and rose petals, wedding guests threw shoes at newlyweds for good luck. One theory is the bride’s shoes were considered a symbol of ownership. The bride’s father gave the groom her shoes to represent the transfer of dominance and, consequently, making it difficult for her to run away. The groom then tapped his bride on the forehead with her sandal to assert his new role.

Another wedding shoe tradition variation was the bride tossing one over her shoulder, which later transformed into the bouquet. In Tudor times guests threw shoes at the couple after the ceremony and if they were hit it was considered fortuitous. Most popular and still in practice is the tradition of tying shoes to the back of the newlyweds’ getaway car.

Sources:

http://www.weddings.co.uk/info/tradsupe.htm#shoes
http://www.koco.com/wedding/2399764/detail.html