I think it is a personal choice and I plan on taking a "need to know" approach. I need to tell an out of state uncle as my next of kin in case anything should go terribly wrong, my next door neighbor in case of emergency, my best friend for moral support and that's about it.
If anyone inquires with what I feel are good intentions, I certainly won't lie ... but if I feel they are going to be less than supportive, I will keep mum about the procedure or give a vague "stomach problems" answer. I don't owe anyone an explanation about what I do with my body.