There's a reason this fragrance has been so very popular. It's because it smells good, is exceptionally easy to wear, and is highly versatile: appropriate for day or night, for work or play, for going out to dinner or for just slobbing around the house. Part of the reason for that versatility, I suspect, is the pure simplicity of its concept: it basically comes down to two equally high-pitched and nasal facets--the sharp musky cedar below and the tart lemon/apple above--oscillating against each other to eternity. The result is a kind of olfactory moire effect, shimmery and (to my nose, anyway) quite pleasant.
I suspect that Light Blue may also carry an additional appeal to Americans in particular, due to the strong hygienic associations of its three major notes, each of which, in their own way, can be said to represent cleanliness. Lemon, of course, is very strongly associated with cleaning products, while that tart green apple note is commonly used in the US to scent shower gels, shampoos, and astringent facial toners. The cedar, meanwhile, brings to mind cedar-lined linen closets or cedarwood chests, used to keep stored clothing clean and fresh and safe from moths. Put them all together, and you're definitely appealing to a desire for cleanliness, or "freshness." I tend to associate that desire with American tastes -- we do love the whole squeaky-clean aesthetic here!--but perhaps it is more universal than I realize.
My one criticism of this fragrance is that it can get a little screechy sometimes. I referred above to both the cedar and the tart fruit facets as "high-pitched and nasal," and while I realize that I'm engaging in an aural analogy there, it's the best way I can think of to describe exactly what I mean. They're both sour, sharp, astringent fragrance types, the sort that can really seem to get all the way up into your sinuses sometimes. Since I enjoy astringent smells, I'm not bothered at all by that aspect of Light Blue, but I can certainly see how it might get in the way of others' enjoyment. That synthetic cedar in the base (is that the Iso-E-Super people so often talk about?) is also extremely long-lasting and tenacious in a stickily pervasive musk-like way --- should you take a dislike to it, you *will* be smelling it for days, not only wherever you sprayed it, but also on anything and everything that got too close to the original spray. You have been warned.
Sadly, while I enjoy Light Blue on other people, it doesn't behave very well on me. When I wear it myself, the lemon and apple notes disappear very quickly, while the cedar becomes *ludicrously* accentuated; the end result is that I wind up walking around for hours smelling very much like a hamster cage. A *clean* hamster cage, mind you, but still very much a hamster cage. So it's not one that I keep around, but I always enjoy smelling it on others. Fortunate indeed for me!, because this fragrance is so very, very popular that once you know what it smells like, you will find yourself encountering it *everywhere.*