I understand they could use the other hack to fill the void. I am referring to actual posts though. The fake stats are just for show. In the actual forums, people get to see what actually exists. If people are looking around a relatively slow site, that displays they have thousands of users and threads/posts, but the forums themselves are fairly empty, it will expose the jig. My suggestion was for those that do use this to keep that in mind.
Try to balance your threads and posts to the stats you display. otherwise, the artificial mods could actually cause your site more harm than good. If people start realizing the numbers aren't "real", they could potentially expose your site on other sites throughout the net. (Especially sites competing with you.

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Don't get carried away is all I am basically suggesting. I can see new admins thinking that adding thousands of users will help their site grow faster. It really wont if the content of the site is lacking.