Hello. I just joined via the EveryTrail app on my new iPhone. Overall, I like it! But I would like to add my vote for having some sort of visual identifier on the website indicating which trips are private. I'd also vote for some form of intermediate privacy option.
For intermediate privacy, you could have hard to guess URLs for sharing in blogs elsewhere (security through obscurity). But it would also be nice to have a concept of "friends" here on EveryTrail where your trips would only be visible to people who you have identified as your friends.
Finally, and the reason I started searching for information online about privacy settings in the first place, I would LOVE it if there were a field right in the iPhone app for determining whether the trip is private or not. Right now, it's public until you go into the website and make it private. At a minimum, I would like the default to be the other way around. (You could have a default configuration setting in the app itself to reverse this.) Or you could simply have a radio button for setting privacy level for each trail you upload -- just like you can define a title, description, etc. before you upload each trip.