There's another common theme that would have killed every one of these sites: marketing. I don't see it mentioned anywhere in any of his site ideas. They all

There's another common theme that would have killed every one of these sites: marketing. I don't see it mentioned anywhere in any of his site ideas. They all seemed to be "build a cool thing and put it on the internet" type of execution. I went through a whole pile of little startups just like this guy, with similar success, before I started to figure out the marketing side of running a business. Once I started paying more attention to "how are people going to find this" than "how is this going to handle [obscure corner case]", that's when my stuff started getting popular and making money. Take any one of those sites, and try actually promoting it to the world. You might be surprised at the results.