delia,
Loved your post. I made a similar point in a thread about sadomasochism the other day. Someone saying they felt like a bit of a "whimp" for not enjoying hot wax play, and I retorted that this is "not the pain olympics". The goal of any form of BDSM is *not* push someone past their limits, or into any realm they don't want to go. It's find a balance that works for you, and that you enjoy. And within that balance that two people find, create a bond of intimacy.
If something goes to far in a person's mind, using a safeword is not failure. It can be a hard thing to wrap one's head around, but it is worth doing. I would never think of a sub using a safeword with me as "failure" myself... it's her I want, the intimate bond with her. The acts we do together are (relatively) irrelevant. We can always find something more to her liking.