For what I've known there are 2 reasons why KYC is implemented on the bounties:
1. To control the greed bounty hunters who uses different altcoin to abuse the campaign
2. To steal your Identity (Identity theft)
The part of KYC that scares me is the identity theft. The way KYC is becoming popular with many ICO projects is also not helping matters. Many crypto enthusiasts are obviously not comfortable giving out their personal details for the KYC process but how long can one stay away from projects that requires KYC verification.