Agreed. I've always said "Jay-Sohn" as well; although I recently saw a job description that was looking for "2+ years of Jason experience"... too bad my name isn't Jason :)
Like Es-Que-El vs Sequel I've heard both about equally and tend to adopt whatever version the person I'm talking to uses without worrying too much about which version is canonical.
On twitter, my ID is JSON and I always preferred "Jason". However, whenever I go to conference that show my twitter handle everybody assumes that is my name and calls me Jason.
