Why now? Because of the changes in her brain, she understands that people and things exist even when she can't see them. This realization is what makes peekaboo so appealing; by playing this game, she gets to exercise her new knowledge of "object permanence."
How it works Practicing the idea of object permanence and knowing that you'll "reappear" may help your baby deal with separation anxiety. Around her first birthday, she'll also begin to build internalized images of you -- storing them in her memory so she can "see" you even when you're not there. Playing peekaboo helps her grasp this new concept as well. So before you banish peekaboo from your vocabulary, remember there's something in it for you, too (a less clingy baby).
Playing on repeat Once babies discover a new game or skill, they'll want to practice it again and again. Burned out on peekaboo? There are plenty of "peekaboo" toys and books out there to give you a break. You can also try squeezing in games during shower time by putting your baby in a bouncer while you pop in and out of view from behind the curtain. Or let your little one watch you hide toys under blankets or cushions, then ask her to retrieve them. Regardless of how you play, enjoy peekaboo while it lasts -- soon you'll have a tot on your hands who won't be so easy to please!