David Lieb

Product builder who turns prototypes into mass consumer products: Lieb co‑founded Bump (a wildly popular early iPhone app) and led the set of photo‑management experiments (Photoroll / Flock ideas) that became the technical and product foundation for Google Photos. He combines hands‑on product instincts with deep technical training in ML/vision to ship consumer AI features (search, face grouping, editing) at massive scale. ycombinator+2

Experienced startup mentor and angel investor: Since leaving Google, Lieb has advised and invested in many early‑stage startups (examples cited publicly include Flexport, Rippling, Skydio, Tally, Rewind.ai). He frequently mentors YC founders and focuses on product, retention, and how to use AI to build products people love. businessinsider+1

Survivor whose life experience reshaped priorities: Lieb publicly shared that a leukemia diagnosis and successful treatment changed how he thought about his career, motivating a return to the founder‑facing, hands‑on work of mentoring and advising early startups rather than running a large organization. ycombinator+1

Strong technical and academic foundation in ML and vision: Lieb completed undergraduate EE/CS work at Princeton and graduate work in machine learning/computer vision at Stanford (research in Stanford's AI lab), giving him domain expertise that helped him apply AI ideas effectively in consumer products. ycombinator+1