As a web developer, I have this almost magical ability to think of a weird thing I wish was on the internet and then make it so.
Facebook for dogs? I can try making that. A ToDo management system? You bet I can throw another one of those onto the pile of ToDo applications that feed the hamster powering the wheel that runs the entire World Wide Web.
Or at least, we as developers have the skills to make some version of those things. What usually happens, though, is that we start a personal project and then it lives on as a half finished ghost town repository in a Github account.