I think it depends where they draw the initial boundary line. If a T has really loose boundaries, there won't be a very big margin between their boundaries and inappropriate behavior - so there really won't be much grey area.

That's not to say that I myself love boundaries or find that they make me feel safe, as others have mentioned. I personally find rigid boundaries a bit unsettling. They make me feel like I must be some sort of monster that T needs to be protected from me. I feel ashamed that there's an assumption that without rigid boundaries, I would invade my T's life and become confused about the relationship. Rigid boundaries make me feel dirty and tainted. So I guess what I'm saying is that I am all for "grey areas" or adjusting boundaries as necessary.