WUOMFM

yik yak

Flickr user Adam Fagen / Flickr

Since it was launched in 2013, the anonymous application Yik Yak has spread across college campuses. Messages are sorted by geographic location and only posts within a mile and a half radius appear.

So it's perfect for saying what you want, about whom you want without anyone knowing it's you, and that is posing problems and challenges for schools around the country.