1. The emergence of a time of sharing "joys and concerns," where congregants would call out (for want of a better term) good things that happened to them during the week, and ask for prayer for relatives, neighbors, themselves for things like surgeries, bereavements, etc. In some cases these seemed to devolve into bragging sessions, i.e., I thank God that my sister got a new job, or, Pray for me as I go on this big vacation, etc. Some churches even passed a microphone back and forth.
2. An expansion of the "passing of the peace" into an all-out "greeting" taking 5-10 minutes where people ran all over the church, shaking hands, catching up, etc., in the middle of the service.
I've experienced both of these at Nazarene, Baptist, Church of God, and Church of Christ (Campbellite) churches. So it's not limited to UU's nor megachurches, although it is curious that they'd leak into the somewhat more liturgical mainline denominations. Maybe the individual mainline parishes that incorporated these were trying to "shake things up" and appeal to people or be "relevant." Seems to be why some Catholic parishes make the peace into a massive greeting period. But IDK, someone else may know more.