People are so desperate to find viable business ideas. We discuss to death MVPs, fake landing pages, articles describing how to find and validate ideas and find first customers. Yet, no one notices when business opportunity stares them in the face. Go and duplicate screenhero. It's not that hard (Screenhero was written by 4 devs and 1 designer). They did YC in winter 2013 and got acquired by Slack in Jan 20015, so it…
You mean you could make a YouTube clone in a weekend? It's easy to fall into this way of thinking. But hey, maybe you will build the next Screenhero, or TeamViewer. Or maybe you'll end up as one of the thousands of other versions of this nobody has ever heard of. The idea is usually not the hard part.
Note that by the time of Slack acquisition Screenhero was approaching v2.0, they had product out far longer than that. So it's not unreasonable to say you could do a v1 of similar product in a year.
Both idea and execution are hard. Cloning existing idea removes one hard part, therefore increasing the chances of success. Look at Excel, Word or Baidu or Sina Weibo.
As to "thousands of other versions of this": you would have to point to at least one. It's hard to argue against imaginary products.
Based on this thread for many people Screenhero has no acceptable substitute.