Protecting identities of participants
The default position is that you should not use people's real names in your research publications unless you have a good reason to do so and you have the express permission of the person to use their name.
What if you are working in a foreign country and the government seizes your field notes? If you are doing research on a sensitive topic, you should encode all your computer files and use pseudonyms in your field notes. That way, even if you records are accessed by others, they still won't know for sure who you are talking about.
If that sounds overly dramatic consider this the U.S. government has started seizing people's laptops at airports. The American Anthropologists Association has warned anthropologists about travelling with field notes on laptops due to the risk they could be accessed by the U.S. government.