I'm working on a very similar site (though also decidedly different), and I can tell you the challenge I've found in that is publisher bias. For example, if I'

I'm working on a very similar site (though also decidedly different), and I can tell you the challenge I've found in that is publisher bias. For example, if I'm looking at 30 technology sites, and sort out by site, the content looks like a fair representation of what's popular in the world -- however, if I sort just by popularity, almost the entire page consists of HN and TechCrunch posts. It's a tricky balance, but I'm also working on it. :-)