Our demographics are the best out there- you can figure out age, income, race, etc of people coming to your site.

We also offer an API where you can call out and receive info on the general demographic profile of a visitor (likely male, likely makes between 50-100k, etc) and then modify your pages in response.

And of course, a sweet real-time lobby display for your website ;)

If you put the tags on your site, you can actually go to the real-time page right now and see the results- no waiting!

Well, Quantcast is free, unlike kissmetrics. And it offers demographics information about visitor composition (ie age/gender/income/etc breakdown), unlike Google analytics (as far as I know). Many companies use both Quantcast and other metrics/analytics services for the differing types of information they offer.

Nothing is free.

Your website becomes a data collecting beacon for their advertising network (hence the awesome demographics).

Nothing wrong with that BTW, it's the same reason Google Analytics is free; but it's worth pointing out.