B-dEsIgN

Layers are misunderstood and underutilized in Illustrator. Many of my Illustrator students, migrating from a Photoshop mindset, needlessly over-rely on layers as a selection technique. Yes, sometimes it's helpful to break down major components of a project into layers in Illustrator. But, unlike in Photoshop, where the underlying pixel-based logic of artwork often mandates that there are no coherent paths to select, paths in Illustrator are easy to select. Add the ability to double-click on all kinds of objects, including not only paths (and, yes, layers) but compound paths, gradient mesh objects, and clipping masks. Breadcrumbs make it easy to keep track of where you are on the isolation path.

Source : http://www.adobepress.com/articles/article.asp?p=1347501