I don't know how it would work as a MR feature, but in places that do create this kind of thing, people do a whole lot of community building and exploring other people's threads, commenting, etc. It would not happen if people were just posting the name and their continuing count, but if people were doing mini-reviews (or longer) it definitely could happen.
I don't see this as competitive in any way--nor do I think we all have to use the same method for it to be personally meaningful and fun. I'm all for fun and reading combined.
