But the biggest issue that spooked investors was the second issue: Apple's privacy changes to iOS. Earlier this year Apple introduced a major privacy feature called App Tracking Transparency (ATT) that allowed users to choose to opt out of third-party app tracking. This means apps can no longer collect data about users from third parties and use that data to better target them with ads unless a user specifically gives the app permission to do so.

Link: Why is Snap stock crashing? Blame Apple and the supply chain
via http://www.fastcompany.com