I thought it would be a great idea, personally. To the uninitiated, a commonplace book is, according to Ryan Holiday writing for Thought Catalog, "a central resource or depository for ideas, quotes, anecdotes, observations and information you come across during your life and didactic pursuits. The purpose of the book is to record and organize these gems for later use in your life, in your business, in your writing, speaking or whatever it is that you do."
He points out that the tradition goes back to some of the greats of Western thinkers (Marcus Aurelius, Petrarch, Montaigne, Thomas Jefferson--and lots of ordinary people besides). For a fundamental philosophy behind the effort, Holiday quotes Seneca: "We should hunt out the helpful pieces of teaching and the spirited and noble-minded sayings which are capable of immediate practical application–not far far-fetched or archaic expressions or extravagant metaphors and figures of speech–and learn them so well that words become works."
Social media platforms seem like a suitable modern tabula on which to adapt the commonplace book (although Shaj Matthew posits a fascinating counterargument at The Millions).
So I've begun a Tumblr microblog called (un)common ground. Though it's not really intended for widespread distribution, it's there and it's public, and I'll probably use it for blogging here from time to time.