The Obama's fist bump

On June third, that special day when Barack Obama announced to a large enthusiastic crowd in St.Paul Minnesota, that he is the Democratic Party Designee, he and his wife Michelle did a little touching gesture with their hands that many people questioned.
What did they do? What does it mean? Why did they each make a fist and touched the fist of their spouse?
My Tennis group has been doing the same thing for well over a year. I guess we copied it from athletes that we've seen on television; golfers do it with their caddies, ballplayers do it with their teammates and friends do it when saying hi to friends. It is a new form of greeting . A new way to say Congrats, job well done. But when the Obama's did it, I thought it was more. I felt that it was a sign of affection of two very close people who have a loving bond between them. I think that fist bump said to me "Job well done and I Love You."
In a similar situation when Tipper and Al Gore showed their own sign of affection with a long passionate kiss (longer than many people felt was appropriate), some people also made a comment. What do you think? Were both O.K. Was one more appropriate? Share your thoughts.