What is the purpose of washing pork?
A book I have (Thai Food by David Thompson - a fantastic book, by the way) suggests washing pork and even blanching in boiling water for any dishes involving boiling/stewing/poaching, as it creates a clearer broth with a clearer flavour (author's words, not mine).

I have found I am less likely to get scum and surface impurities in the dish as it cooks.