Gnosticism has been around since the early Christian church, and their doctrines started to creep into the early church and confuse people. In the grand scheme of things, their major ideas and doctrines were combated with Scripture by some of the notable church "fathers" like Tertulian, Martyr, Iraenaeus (sp), etc... It's nothing new, but I wouldn't be surprised if they became popular all of the sudden in today's times.