There are plenty of exciting articles out there about reflectors. People will cover themselves with all sorts of funky reflector materials, just in case.
I tend to see reflectors as a last-resort. If I'm having a really bad day and forget to turn on my rear lights.. or if I run out of spare batteries... or if my light failed and I didn't know it... I'll probably be seen. But I don't see them as a solution to being seen at night. The important thing to remember about reflectors compared to lights is that they don't manufacture light. All they do is concentrate it. All reflectors, regardless of design or construction, create a "hot spot" of returned light that is hopefully near the source of light.
This means that in foggy situations, reflectors perform much worse than lights, because the light to the reflector is being absorbed by a certain amount and then the return beam is also being absorbed by the same amount. This also means that if the light is not coming from the right angle, it won't bounce back properly. This can be as simple as a car approaching with the passenger-side headlight broken. And people with cars forget to put their headlights on all the time.
On the other hand, just because reflectors only work sometimes doesn't mean that they are completely useless. Much in the same way that cars are required to have reflectors and lights, I think the trend of making bike lights that do not have sufficient amounts of reflector space is dumb.