Total tangent: In the last 30 days, I've had more page visits from Google by people searching for "Joe Kim."
Is that a good thing or a bad thing? There are so many people out there who are named Joe Kim that I have no idea who they're trying to find. The average pages/visit is 4.17 for Joe Kim and 1.76 for Joseph Kim. The average time on the site for Joe Kim is 10 minutes while the average time for Joseph Kim is only 4 minutes.
Here's the bottom line: more people go by the name "Joe" even if their legal/technical name is "Joseph." So, it's more common for people to know someone called (not named) Joe Kim rather than Joseph Kim. There's my 30 second thesis on this issue.