Curt Ebbesmeyer had Bill Blazek and Margie documenting drift shoes for a while. Margie notes: Bill may still be doing it, but I quit after about three years. Curt was interested in whether certain beaches attract left or right shoes. I collected over 500 shoes and kept a spread sheet with an entry every day I found any drift shoes. My data showed no statistical difference between the arrival of lefts and rights, but Curt eventually concluded, from what data I don't know, that there are left and right beaches. If I remember correctly, he mentions it in his book. I know I've heard him say it in a talk.
Curt is the keynote speaker at this year's Sea-Bean Symposium, so I'll be sure to ask him. Meanwhile, there are pages and pages of Internet "hits" for Curtis Ebbesmeyer - here's a good one that talks about his shoe theory.