Summer 2012: Waze Doubles Its User Base To 20 Million In 6 Months
Eric Barker stashed this in Diabolical Plans For World Domination
1. Word of mouth. Its users are rabid and they tell other users to get it because Waze is useful.
2. Social. Easy to share updates on Facebook and Twitter.
They also did some partnerships with broadcast TV that helped them get to 10mm users.
But 10mm to 20mm is all word-of-mouth and social, it seems.