I think, as far as strength is concerned, what's important is not how many people join it, but how many people actually stay on it. I mean,the main USP of this platform is that posters get paid. In that sense, its more of a blogging platform with a social network attached to it. So ultimately, if the payouts are satisfactory, the people will stay(and more people will join).

The payouts obviously depend on the amount of Steem purchases. So I think what's important, is that the market shouldn't become so competitive that those who want to promote their posts can't afford to do so.