Maybe I see things differently, but using a safe word is for emergencies only and is something that I feel must be in place but would rather not hear. It doesn't mean failure of My submissive but more of failure on My part to see and pay attention to other physical and emotional signs.
The safeword is suppose to be a last resort- meaning that if I don't pick up on the discomfort then the submissive is to alarm Me of it verbally. I've only had one submissive use it and when it was used it was used out of fear of something new and prematurely.
I don't take the use of one lightly but I also expect to be alerted by it when necessary. The use of it shows respect to the relationship and also to one another and I would probably punish My submissive if she didn't use one when needed. It may be looked at as double punishment but I look at it as a lesson needed to be learned deeply and thoroughly.
Knowing your partner is essential and boundaries should only be pushed if all parties are aware of that push. Pushing, scare tactics, and other Dom/me selfishly inflicted acts shows that the Dominate is still pre-mature and not reading for that responsibility-Trust. I hold it in high regard and keep that in mind in scenes... and out.