He introduced me to a term I had not heard before (but a problem that I am far too familiar with).
The Term: Migratory Flock!
The Definition: People that move/migrate from flock (church) to flock (church). When they arrive at your church, they tell you how terrible their last church was. Then, slowly, they will try to influence you to change your church to become what they want it to be. Then, give it about two years, and your church will become the "terrible church" they left! That is how they roll. That's the pattern of the migrating flock.
The best thing that you can do is to encourage them to "sense the Lord's leading to a different church" than yours. And stay the course on the vision God has given you.
Also, beware of the "local-church-flavor-of-the-month-seekers." There are plenty of folks that hop around to whatever is the current popular flavor. Remember, God is at work using all kinds of flavors!!