I used Alexa.com and based the percentages off reddit and Hubski. It's only speculation, though. I'm just hoping somehow the actual statistics are revealed to see how close I am.
From what I can tell about "active" contributors to discussions, it's 19% Detroit. 35% North Carolina (thenewgreen) and 25% California (kleinbl00) As for 10% Canada, that's mostly theadvancedapes who is very active on these pages. He's from Toronto, but currently - what ho? in Brussels. It must be Tuesday.
Sorry about that. I'll try to be more serious. It all depends who populates your feed I guess. There's dark and dirty corners of hubski that I never visit. For example, any tags that say #reddit never enter my feed. I also muted #circlejerk - I've always found that term kind of creepy.
That's 'cuz mk & thenewgreen have this idea that you should follow people, rather thank tags and I think if you look up "popular" on the page you end up following those who already have too many followers. By way of perspective I'm following three people, but like 20 tags.
I'm all for following tags, I think it's a great way to discover people. In my opinion the best way to use the site would be to follow a good number of tags that interest you and then begin introducing people to your feed.