Another one from rpg.net, courtesy of AikiGhost:
Is it ok to cane your submissive till they use their safeword just because you want to take them past what they can handle?
I went back and forth on this issue for quite some time. On the one hand, part of the submissive fantasy is being out of control, and possibly going past what you can handle. Furthermore, the whole reason you have a safeword in the first place is to put a stop to something that is going too far. On the other hand, just because you're submissive doesn't mean you automatically consent to everything your dom tries to do to you, and if you've already established and negotiated a certain pattern of interaction, then suddenly and unilaterally changing the rules might feel like a betrayal, even if the safeword is uttered.
So, on the balance, I wouldn't. What you should do instead is talk to your partner. I know it doesn't seem as sexy or dominant to do it that way, but presumably, this person you're caning is someone you care about, and the trust you've established in your relationship is far too important to risk. The fact is that there are only a limited number of reasons not to discuss this in advance.
Either you are too embarrassed to admit your true desires, which seems unlikely to me, and in any event unnecessary (seriously, this person is letting you cane them, I doubt that there is much that would shock them). Or you really want to do this, and you're afraid your partner won't go for it, in which case the need to talk is doubly important (the "it is better to ask forgiveness than beg permission" philosophy does not apply to sexual activities - even when dominance play is involved.)
Or, you might sincerely believe that not asking first will make it better for your partner. I can't say that you're wrong about this, because it certainly seems plausible to me and you would know your partner best, but even under this best case scenario, you're still not letting your partner decide for themselves, and that can be infantilizing. Your partner is an adult, and they deserve a chance to own their own sexual fantasies.
Nonetheless, if you do go ahead without talking about it, my advice would be to tread carefully. At the start of the session, warn your partner about your intent to push their limits and take your time ramping up the intensity. That way, if they discover they like it, they will feel like they had some collaborative stake in the experience, and if they don't like it, they will not feel as if you ambushed and trapped them into doing something they didn't want to do.
Above all, remember that the key to any grown-up relationship is mutual respect, and that being a submissive involves a massive amount of trust. It is your job as a responsible dom to be worthy of that trust.