One of the toughest things parents often express to me is the difficulty it is staying current with wide variety of applications their children are using. Things do move fast but luckily you don't have waste hours trying to determine if it's ok for your child to be using the newest app that "everyone" is using. Many parents willingly admit they lost track long ago but fortunately for those in both of these cases their is help just around the corner.
Safe Smart Social, https://safesmartsocial.com, is a great resource for parents, youth leaders and educators who want anything from a quick crash course in which apps are ok for teens to use to a compete professional social media audit. If your teen has a mobile device you need to check out the Parents App Guide on his page. You can also sign up for a free Social Media Webinar which is held each week.
Once you get caught up, follow him on twitter or subscribe to his feed so as things change (and they will), you will know in time to protect your kids.