For Information Today, Richard Poynder recently interviewed Peter Suber about his role in open access (OA) advocacy, the successes and progress and challenges of OA approaches and initiatives, and the contours and trajectory of OA as movement. In its breadth and detail, the interview provides a good overview of OA generally and of Peter's work and role in advancing OA.
Here is Peter's top-level take in the interview on "why we need OA":
Authors need OA to reach all the readers who could build on their work, apply it, extend it, cite it, or make use of it. Readers need OA to find and retrieve everything they need to read and to allow their software prosthetics to process everything they need to process.
OA doesn’t merely share knowledge. It accelerates research by helping authors and readers find one another. It’s compatible with intermediaries but not with intermediaries who erect access barriers to keep authors and readers apart.
The whole interview is a worthwhile read. Check it out!
(And there's plenty more OA-related posts, talks, videos, etc. to explore via the right-hand "related content" list.)