[Anaraxes]

Yes, it's mostly to have an excuse for tucking away rituals in underground chambers, old churches, and dark catacombs.

"Spectate" doesn't simply mean "line of sight", as from across a battlefield. (Or another planet.)

And I think even "choosing to participate" is a bit thin, not least because that's one-sided while a ritual is a group activity. (If it weren't, the inclusion of some naysayer would be at worst non-contribution, not a negative effect.) It'd a lot more interesting if the saboteurs at least have to try to infiltrate the group or get picked up in the "meh, c'mere and gimme your energy point" presses from the overbearing Wizards' Guild of the dystopian city when they don't bother to do screening, rather than just having the Resistance sitting at home announcing"I oppose all rituals today" each morning when they arise.

It's a lot more likely that there's something like an Area variant of Lend ST involved in ceremonial casting. You'd at least have to get into the ritual area to be a subject of the draw. Once you're involved the magical field, then you can oppose it. "Involved in the magical field" could be a lot more elaborate. (Much as you can target unseen people by describing them, it would be consistent for a careful ritual leader to more carefully target his FP batteries -- but that's just the sort of place a lot of people cut corners when there's no reason to think there's a potential problem.) Just being able to resolve the figure of the caster on your retina isn't much of a magical connection.

Of course, the requirements and effects aren't defined in that kind of detail, so GMs can do as they like.