I'm on F.B. but never realized they had cruise groups, shouldn't surprise me though. We pretty much hang with CruisingCM and Ewoodspark's take on this. Back in the days when you had no choice but to book traditional dining we really had no problem with table mates as a rule, let alone "clingers" but were aware of a lot of horror stories, so when "anytime" dining came about we hopped on, and like that so much better. Two reasons mainly, you never know what type of weirdo's you may get as table mates so we go table for two only and since we cruise for long durations that would be catastrophic and secondly, we don't like to be relegated to a specific time to eat every evening.
Sort of similar though, is one of our favorite cruise events which occurs on Regent, it is their "Block Parties". One per cruise segment. Your neighbors don't enter your cabin, rather, at the call, everybody grabs their wine glasses and enters the corridor. Then the crew races through the corridors pouring top quality wines, red and white, and others carry trays of delicacies, Hors D'oeuvres, then the Captain comes running through shaking hands with everybody, and yes, everybody, plus the real captain not some staff captain or hotel captain, the real McCoy. Most guests stand out in the hall for a bit afterward, chatting and then return to their cabins. Sure is nice to get to know those around you in adjacent cabins.