I've got to go with what seems to be an emerging consensus: Safewords are not necessary in all cases, but they are strongly advisable if not necessary in some.
The worst that could happen for someone who misreads cues includes not just being tickled too much, but the fallout from that which could involve emotional trauma or physical damage.
MTP Jeff said:
assuming that you could breathe, and that you were not literally having a heart attack, what would happen if you were experiencing this and the ler kept tickling you anyway?
I don't know how relevant that question is. Emotional trauma is is still possible. And heck, a lot of people have heart attacks
themselves and don't even know it. While it's unlikely to occur, if it did, it's entirely possible even an experienced 'ler wouldn't recognize it until the damage was done, or perhaps it was too late. Plus, some people, being tickled, are prone to hyperbolic statements which ironically, are not real cues to stop: "You're killing me!" "You're going to give me a heart attack!" So, do you assume it's hyperbolic and keep going, because it's "just tickling", stop because it
might be a cue, or keep a safeword on hand for the event that they recognize something real and dangerous is occurring? (Again, the way around this conundrum is practice, knowing your 'lee and what behavior acts
as a safeword.)
I don't think the idea of "needing" something to stop should end at, "Do they survive the experience?" Or, "Do they smile as they leave?" Because, yes, people will survive a great deal of punishment, and yes, many will leave with a smile out of courtesy, but will never be willing to do something like that again, after having been pushed that far.
I like to use safewords at the beginning because people react differently, and you want to learn their signs. But once you understand how they react, safewords can be mostly discarded, because their signs act
as the safeword. Keep in mind though, that these signs can emerge before any demonstrable signs of serious physical distress. Now, one could also ask of these signs, "What's the worst that could happen if you tickled them beyond that? Someone gets tickled too much." But there's of course an ethical issue of going beyond a person's tolerances if they're unprepared or undesirous of it... I think it should be recognized that however much it's "just tickling", it can get truly unbearable just like anything else that is forced upon someone, and one should watch closely and act empathically to the needs of the 'lee. More extreme limit-pushing should be reserved for the more advanced levels of understanding your 'lee.
The areas of want and need to stop are always a bit hazy, but are best clarified with a good relationship between 'lee and 'ler. Absent that, safewords are key, and a good place to start for beginners just learning about each other.
I don't think that because there are those in the world who shouldn't be involved in or are too irresponsible for power exchange that that in any way invalidates the use of safewords. It only means these are not people to be played with, regardless the safeguards put in place, and safewords with them do not make one safe. Trust should be reserved for people, not procedure. And I'd hope that's just common sense.