Yes, at this point they are ubiquitous. But have you wondered how they get them to lay so flattering? They get rid of the excess fabric so it lays narrow and thin across your neck (or head, or waist) This also allows you to stretch the fabric out more to get a better fit.
It's easy to make your own flattering bandana scarf (I have several in different colors and thicknesses, at $11 for twelve different colors it's a style steal)
Watch the video below and then behold the results of my oh so arduous (not) labor.
Wearing: Sweatshirt, DIY Bandana Choker, Nameplate Necklace
For the DIY: Scissors, Iron, a magazine/ruler, no sew hem tape (optional), bandana