I don't think we need to get into blurring etc., nor get over-paranoid. I don't see that there is any kind of problem with pictures that include people in normal situations.

If someone has taken a picture of me sailing my boat, I wouldn't expect to be asked for my permission before it appears on our club site. But if I was lying naked on the deck (not a pretty sight!), then perhaps i would.

Another situation would be a photo of boats moored up. There might well be other people in the shot, e.g. standing on the pontoon next to other boats. We have no idea who they are - does it matter if they appear in shot? I don't think so, again provided there is nothing embarrassing in the context. Blurring faces for the sake of it would actually imply there was more to the picture than meets the eye - the opposite of the intent!

It's all a question of context. The poster should consider if the picture is potentially embarrassing, if so then either get permission or don't upload it.