Share something you're excited to be building on the Internet and you will invariably get one of three uninvited responses (or all three): 1. I did that already a long time ago. 2. You could do that much better. 3. Here is a bunch of prior art. If your first impulse is to reply with any of these, maybe ask first! Some people may value these inputs at some point in their creative process. Others will find them deeply demoralizing.