Moderator: Lawrence You
Panelists: Don Marti, Raptive; Miguel Guevara, Google; Greg Chappell, Privacy Angel Investor; Ari Levenfeld, Google
The "privacy" offered by "privacy-enhancing technologies" (PETs) on the web is remarkably different from the privacy that users want and expect. People seek out privacy to avoid real-world privacy harms such as fraud and algorithmic discrimination, and PETs, focused on more narrow mathematical goals, can actually make the real privacy problems worse and harder to detect. Can today's PETs be fixed, or should the web move to more productive alternatives?
Lawrence You most recently worked as a director and privacy engineer at Google, where he led a team that developed core business practices working across software development, research, data management, legal, compliance, incidents, and investigations teams; during his earlier years, he led storage and log analysis teams. During Lawrence's career, he has worked on large-scale data storage, platforms, and development tools. He has supported PEPR as a volunteer and served as co-chair in 2024 and 2025.
Don Marti is VP of Ecosystem Innovation at Raptive (the company that used to be CafeMedia), and a former strategist at Mozilla and former editor of Linux Journal. He works on web ecosystem and business issues including collaborative research on the impact of advances in consent management and tracking protection technology. He started the California authorized agent project at Consumer Reports Digital Lab that led to the the development of CR’s Permission Slip service. Don has written for AdExchanger, Linux Weekly News, and other publications, and co-authored a paper on the economics of software quality for the Journal of Cybersecurity and a book chapter in Advances in Advertising Research.
Miguel Guevara works at Google's Data Protection team, focusing on implementing privacy-enhancing technologies at scale and launching new initiatives that further overall privacy.
Greg Chappell is a software engineer and angel investor with over 20 years of experience at leading technology companies. Most recently, he worked on AI Responsibility at Meta, where he served as the senior engineer leading efforts in targeted AI transparency, youth advertising, and user data governance for large language model (LLM) training. Prior to Meta, Greg was a Principal Engineer at Amazon, spearheading initiatives in AI Privacy, and held engineering roles at Microsoft.
Today, Greg focuses on angel investing, partnering with early-stage startups at the forefront of privacy, security, and responsible data innovation. He holds an M.S. in Computer Science & Engineering from the University of Washington and a B.S. in Computer Science from Rensselaer Polytechnic Institute.
Ari Levenfeld is the Global Head of Ads Privacy for Google’s Government Affairs and Public Policy team. He has spent the last 20 years working for technology companies, focusing specifically on privacy, global compliance, data protection and policy. Prior to Google, Ari was Chief Privacy Officer for a number of digital ads and AI companies including Quantcast, Sizmek and Rocket Fuel. Ari holds a BA from the University of California at Santa Cruz, and a Master’s degree from the University of Southern California. He served as an NAI board member for 5 years and co-Chair of IAB Europe’s Transparency and Consent Framework Launch Committee, which he helped to create. Ari has published extensively on public policy related to digital privacy, and holds several ad fraud and abuse prevention technology patents.
author = {Lawrence You and Don Marti and Miguel Guevara and Greg Chappell and Ari Levenfeld},
title = {Panel: The "Privacy" Offered by {PETs} and the "Privacy" That Users Want. Why So Different?},
year = {2025},
address = {Santa Clara, CA},
publisher = {USENIX Association},
month = jun
}