Well, with thanks to GreyHawk613 and NanCycle, I have my answer.
The user "removing a friend" gets an "are you sure" message and then the removed friend disappears from your profile. The ex-friend just looses you without any notification at all.
So, if you no longer wish to have certain friends on your profile, you can delete them stealthily and you will be relying on them noticing that you have gone!