Format- players get to place their ball within 1 club length of selected ball (while staying in a similar situation) and play their next shot.
Is their ball in play as soon as they place it, after they address it or, like a tee shot, not until a stroke has been made?
i.e. Player places ball, addresses it and
A decides that he wants to move it while still staying within 1 club length of the original ball. Is the player penalized if they move their ball?
B's ball moves after he addresses it but before a stroke has been made. Penalty?
In my opinion, given the loosey-goosey nature of a scramble, a ball should not be deemed to be in play until a stroke has been made on it.
According to http://www.usga.org/RulesFAQ/rules_answer.asp?FAQidx=126 the ROG don't apply to a scramble and it is up to the committee to determine the rules (but I have seen some scramble rules sheets say that USGA rules apply except as noted).
If you were on a scramble committee, when would you deem a ball in play?