A VC: Three Statistics That Lie
avc.blogs.com
avc.blogs.com
Anyone with info on this want to clarify?
i do know that i've in the past used a WP plugin on a blog that definitely counted uniques.
http://www.problogger.net/archives/2007/08/16/why-does-my-fe...
There is an explanation by Rick Klau who is (was?) Feedburner’s Vice President of Publisher Services.
Hope this helps.
In the most significant cases, the readers actually report back to FeedBurner how many subscribers are using that reader. For example, Google Reader. In the user agent string, Google Reader (as well as, I believe, Netvibes, Newsgator, and a few others) says "X subscribers", and that number is then used by FeedBurner. You can check this out yourself if you have access to web stats on a domain that hosts feeds. Check them out. You get to see the same numbers that FeedBurner puts on their charts.
With non-Web / non-centralized readers, it gets trickier, but FeedBurner uses IP addresses combined with user agent strings to get an idea of what's a unique reader requesting multiple times or not. Typically this system works well and isn't wildly inaccurate.