I don't think we've made any graphs of user growth here. One of the things we want to be able to do is give users the ability to make Hubski feel like a small community even when we do grow to the point where this article says we'd start to have problems. One of the prevalent pieces of advice for improving your reddit experience is to find small subreddit communities for things that you like and just subscribe to them. Hubski has even been described as a "like a really nice subreddit". You have to ask around to get that kind of advice, though. When you first start out you're just thrown into the mess of defaults and an alternative experience isn't shown as an option. Hopefully we'll be able to accommodate different user experiences, from those who want to feel like they're a part of a huge community, to those who just want a quiet space to discuss their few niche subjects.
I tend to look at hubski as a bit of a /r/maturediscussion. I'm not even sure if that sub exists, especially considering that it's reddit and the sub would be quickly vandalized by trolls. I think hubski will always be small, unless significant changes occur. I don't want those changes to occur. We've had significant influxes with thousands of new people visiting the site, but only a few stay per thousand. That shows hubski can't appeal to the masses in its current form--a good thing. Anything that appeals to the masses is simply increasing its odds of failure; once you appeal to everyone, you appeal to nobody on a personal level.