Well, the "victims" can open a lawsuit if they want, but I don't think Snapchat is liable for foolish behavior. Driving safely is a driver's main priority. The driver can be surrounded by many distractions in the car, CD player, radio, smartphone, magazine, book, mail, etc., but he or she is not to do things that would cause an accident. You can have a donut in your car and stare at it for five minutes. You'll probably crash, but you can't sue Dunkin Donuts. The liability is on the driver. You can have a GPS app but if you are looking at the screen and not the road, and you get in an accident, the driver is at fault. Garmin has probably faced some legal action due to driver stupidity.
The fact that they admitted to going 100 MPH tells you that the driver was recklessly driving, even if he did not have the snapchat app running.