01/2020: Here's a documented though critical history of PGP, with insightful links. Providing several consensual (or at least presented so) arguments and documents, the author argues that PGP is dead. However, the article ommits to mention that 2019 witnessed the emergence or fostering of interesting projects (Sequoia, keys.openpgp.org, Pretty Easy Privacy). Moreover, discussions are still very lively and the IETF standard is still being continuously edited. Still, I find this article very usefull to have a bettir idea of key moments in PGP history.