Immoral or not, it depends on how we see it. There are laws prohibiting unfair or deceptive practices in advertisement, but they are different in different countries. But is showing your real wins on slots unfair or deceptive? I don't think so. As with any other advertisement, it is we who can make it harmful for us, not the ad itself. Ads are annoying sometimes, and in other times they make us buy unnecessary things, but the world would be less funny without them. And these big wins on slots, in particular, some of them are really fun to watch.