How is that powerful? Any mobile app has geolocation data. How is that a market differentiator? That's like saying they have mobile OS targeting... So?

Few other apps that I'm aware of provide live advertisements for events happening nearby as part of your natural use of the app in a really noninvasive way, and provide incentive to share those advertisements.

Snapchat geofilters are non-invasive and will be seen in normal app use, but don't really bother you. They can inform you of events happening nearby or, if you're at an event, you can use the geofilter when snapping, which shows your friends that you endorse the event/product/whatever, in a totally transparent, opt-in way. That's super powerful.