I have some issues with this topic:
Like I wrote in the comments I do welcome answers like that from @nhinkle a lot, especially when it comes to gear. Still it's not answering the asked question "Why one needs strong headlamps" and because of the high quality of the answer it's on first position now.
I vote to split the topic (by a moderator) so we have a new question like e.g. "What does the 'Lumen' specification on headlamps mean?" or maybe better "Is this headlamp really as good as a high end item 10 times more expensive?". Nhinkle's answer would fit better then.
Also I don't favor to create a tag on lumen because this is simply too narrow/specific for TGO. It fits great on physics or engineering but we won't get enough questions with that tag on Outdoors. Also it's not that relevant here. A tag like headlamps suits that very well.
What do you think?