I sent this to a few dozen friends:

Hello. I’m writing to you about Facebook profile “xxxxx xxxxxx”. 30 of his 100 friends seem to be mutual friends with me. This includes you. I think it’s a Russian profile used to track me because I’m a person of interest (journalist and American businessman) in Ukraine. I don’t post anything secret on Facebook. All my posts are global. But nevertheless, please consider unfriending him.