It could also fail miserably if not executed properly, which is the more likely result. If your idea really is as good as you say it is, then revealing it won'

It could also fail miserably if not executed properly, which is the more likely result. If your idea really is as good as you say it is, then revealing it won't ruin your launch. In the end, it will get copied if and only if it's worth it. And that will be determined by your site's execution and relative success (or failure).