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Next, many of the FE and meet n greet lists have a last name, age, where you are from, if you are celebrating anything special, if you have dietary needs, kids names and ages, etc. One of the amazing things about these groups are the connection you make and the friendships you forge. On the other hand, some only want a forum to ask questions and get info about cruising, ports, when pirate night is, dining rotations. Etc. The DIS boards are perfect for that
BUT other people want something more. That's what the other places offer.
You're right to say that keeping things private vs. public is challenging on the Internet. Because google docs and FB can be closed to the public, the groups can be set up as private, and to different levels of privacy. Mostly, they are by invitation or referral only.
I like those avenues in addition to DIS board because I don't want to have info on this public page as to when we will be on a trip, how long we'll be gone, etc. From talking to others on the cruises we've been on, they also like the flexibility to be as anonymous or connected as they like.