People who are running marathons for charity are ordinary people raising perhaps a few hundred pounds. There's too many people running in them to publicise them all.
Beckham is a multi millionaire whose every fart will cause publicity, and no more so than the press conference today which gives him centre stage to say: 'What a good soul I am!'.
Even if that is the case there will be some ordinary people who will fund raise to say the same thing to those who are local: 'What a good soul I am!'. It is just that is said on a smaller scale because they are not a celebrity.
To me, David Beckham is no different to any other person raising/ giving money to charity because I do not personally know him. So I have no idea if he is doing this for the publicity or not. I'm just focusing on the charity aspect which is the main thing. If he wants to use it as a publicity stunt that's fine with me. I'm just not going to be miserable about it.