Interestingly, this bubble is <i>not</i> powered by ads. Only one of the top 25 &quot;unicorns&quot; worldwide, Snapchat, is ad-based.  The others provide a good or service paid for directly by their customers.<p>[1] <a href="http:&#x2F;&#x2F;fortune.com&#x2F;unicorns&#x2F;" rel="nofollow">http:&#x2F;&#x2F;fortune.com&#x2F;unicorns&#x2F;</a>