Besides, I don't know about others, but I've recently put out multiple job ads for one vacancy. Our app, Noctacam, uses computational photography to take great photos at night. I was looking for someone with computational photography knowledge and/or iOS. And/or Android, since we plan to make an Android app in the future. I found it convenient to post three job ads, so that I can clearly organise the dozens of applicants based on their skills. Two of them went unfulfilled. Which is exactly as was intended. Someone who doesn't understand the background may say, "Oh, no, tons of positions aren't being filled." In other ways, it may a counting problem, not a real problem.