We've yet to find a way of saying "That's not appropriate to discuss with you" that doesn't either sound a bit rude or make the other person feel bad for asking, but we had an encounter recently that has made us wonder whether other people actually feel the same way as we do about the importance of privacy and confidentiality in fostering.
We were at the station with Jack-Jack in the buggy, and a lady with a baby of a similar age came up to us and asked what make it was. We chatted briefly about the buggy, and then out of the blue she volunteered the information that the baby with her was a foster child. "Oh right, we're also foster carers," Esmeralda said, smiling down at Jack-Jack. We never normally tell anyone we're foster carers unless it's specifically come up in conversation or we're asked directly (and sometimes not even then depending on the situation), but the lady's next question was just asking which agency we were with, which was fine. We told her, and found out that she was with a different one. She seemed pleasant enough, but the rest of the conversation completely floored us:
Lady: "So are you going to adopt him?"
Esmeralda (red flags up, looking up at the train times): "We're not sure."
Lady: "Oh, what's going to happen to him then?"
Esmeralda (wondering what to say, checking whether Jack-Jack is listening): "We're not sure."
Lady (oblivious): "We're concurrent planning with this one. It's not definite - his mum's a drug addict and his dad's in prison and they're contesting it, but we've been told there's no way his mum is ever having him back. We've got a new one arriving any day now too."
We are always very careful what we talk about in front of Jack-Jack with regard to his parents, contact, his future etc. but even aside from that, we wouldn't have had the above conversation with one of our friends, let alone someone we don't know. Not even our close family know anything about Jack-Jack's history. The lady's little one was listening intently and there were lots of other people on the platform milling around. We've been asked whether we're going to adopt Jack-Jack and what's going to happen to him plenty of times, but to have been asked this by another foster carer, a complete stranger, who then volunteered information that should be confidential about her own foster child made us feel really uncomfortable for quite a while afterwards.