We know that MEMS is replacing quartz. But why? And why now?

MEMS (Microelectromechanical) oscillators were first introduced commercially six years ago. Now MEMS is making significant incursions into what was once the exclusive territory of quartz oscillators. Why is this transition happening now, rather than ten years ago or ten years from now? The transition has been paced by the MEMS community developing the necessary high stability, high frequency, high Q, and high output resonators. Also, MEMS oscillators rely on advanced circuit architectures, particularly leveraging fractional-PLLs and precision temperature sensors. These specialized circuits have only recently become sufficiently small, low noise, power efficient, and accurate.