Proximity of corals to one another

[Itchy Trigger]

So as I'm adding corals to my tank I'm being very careful to leave plenty of space around each one, accounting for future growth, as well as the potential for LPS to sting one another, etc. But I'm wondering... I see many pics and videos of reefs in which the corals are much closer together than I would have thought would be advisable. Are these people just lucking out? Or perhaps I've overestimated the amount of space each creature needs?

[dustinmccrary]

My green star polyps zapped my acans. I didn't know they were that dangerous.

[Reefenstein]

I didn't know GSP would do that!