I often Merit users who don't post again after their first post. They come here to solve a problem, and after they're done, they don't need the forum anymore. Those aren't the best users for the future of the forum, but they are genuine (Bitcoin) users.
Yeah, this seems pretty common. They probably don't even understand the merit system, but I still think meriting these types of posts might actually encourage new users to stick around. At least, I'm hoping so. Though, I think most of my newbie merits are the types which come ask a question, and then leave indefinitely.