Business model: 2 GB free to users; they charge for additional storage.
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Where They're Based: San Francisco
What they do: Pronounced "discuss," Disqus allows users to track the comment threads they participate in, on websites across the Web, all in one central area.
Quote from cofounder Jason Yan: "With Disqus, immediately, I see all the comments I've left across websites and I can see when other people replied to [my comment] without having to check out each individual website all the time."