I agree that solemn rituals are harder but more powerful. I don't think doing a pin-prick-blood ritual is an inherently bad idea, but it's the sort thing that's too creepy to be used in any kind of ceremony that we wanted the public to know about.

Beyond the creep factor, it also (slightly) crosses a line that I don't want to cross - causing bodily harm. There may be genuinely good reasons to cross that line, but once you've crossed the line then a lot of issues become a lot murkier. Since we're dealing with complex and potentially dangerous forces, I'd rather set up some strict rules that are well in advance of anything genuinely bad that might happen.