Agreed. I play most of time as SL and there really is some sensitive situations where I would rather act alone for moment. For example, trying to crawl over open terrain with very little cover, it's bit bad thing if someone spawns on me and starts running around. Or even if he stays low, he will anyway be on standing position for millisecond and so exposing both of us. Ofcourse I always say about it, but there are always people who don't listen or read chat.
But I think this feature should be with timer. It would prevent idiots from keeping their spawnpoint always locked.