There's definitely some pressure within social cliques to identify as such. A few scholars within the past year have pointed out that this rapid increase in identification bears hallmarks of classic social contagions. Broadening definitions have certainly increased the numbers. I remember being told growing up that "Queer" was an offensive slur, and now there's a massive group who identify as such. At the same time, I've yet to receive a concrete definition of what that really means, and the nebulosity of it leads to conflicting people assigning different standards for meeting the threshold. I'd love to see some longitudinal studies about where people who identify as LGBT today end up a decade from now, but that's obviously going to have to wait.