Thanks for your comment. I agree that with FTFs there are some borderline cases that cannot be sorted out in a way that satisfies all. Your last case is an example of this, but I do not think that this causes a major distortion of the statistics.
Years ago we had FTF statistics here in Belgium which were extremely strict and went like this: as even in cases where several people are looking for a cache at the same time there is always one who really finds it first, only one person could claim an FTF for a given cache. These statistics were done manually, and where there were more people claiming an FTF they had to sort out themselves who was the real first finder. Obviously, with the increase in new caches, it became much too much work to keep the database up to date, and therefore it was discontinued at some stage, especially as the wonderful statistical tools of PGC became available.
This former Belgian approach was probably too strict, and I agree with your remark that there are instances where several people would legitimately claim a Co-FTF. However, the observation from my experience on this it that again these are rare cases – especially if we are talking about more than 3 or 5 people – which do not distort the statistics, while the mass FTFs at events clearly do so, to the point of making them meaningless. I agree that it would be difficult to find a limit that would satisfy everybody, but perhaps 3 or 5 FTFs on the same cache would be generally considered a good compromise. (Of course, developing further the idea of the tick box, one could imagine this to allow personal limits like "include mass FTFs" with less than "x" FTFs where you could chose your favorite value, but I assume that this would be very difficult to implement, wouldn't it?)