Quantcast.com is the ultimate source for website demographics. All data is available instantly, free, & without logging in. This data is crucial when identifying your target market for your product or service. For example, if you are considering getting into the sporting goods/knife business you could look up Thompson Outdoors on Quantcast.com. You would learn what the target market is for this range of products. Based on this you could determine such aspects of your marketing strategy such as which websites would be the best to purchase sponsored links or banners on.
I used quantcast for about 6 months and finally stopped using it. A few weeks ago they changed their code up without telling anyone. So my site stats went to 0 hits. Finally I figured out what happened. Also, a lot of the sites listed on quantcast are estimates, not directly measured. Some of the sites I am competing against are showing 2X the hits my site was - and I was running their code. Sometimes my ranking would drop by 20,000 places over night. One of my main sites would go from a #85,000 rank worldwide to around #110,000. But other sites that were "estimated" would stay in the same exact spot while I dropped back? Something is wrong with that picture. Their changing the code up and not sending me an email was the last straw, after that I left. Ok, so what?
Adding the js file is a turn off. I don't want another tracking script along with analytics. Every extra file will slow the pages. Since most webmasters think that way, most sites on QuantCast are not quantified--so QuantCast wont be showing actual results. If they could get rid of that, I would love to use it more.
Quantcast slowed down my page loads about 1 - 2 seconds. The impact of the script on page loads was almost nothing. I do not know where you get "quiet a bit" from?? I do not call 1 - 2 seconds a lot. If they would have at least set out an email saying they were changing their code up I would have stayed with them. I have not used quancast in almost a month and my rankings are the same right now as when I removed the code. http://www.quantcast.com/survivalistboards.com
1-2 seconds in load time is a huge deal actually for sites that deal with lot of operations; specially dynamic sites.