Alexa

I feel Alexis are more concerned with results that putting the satisfaction of there customers in mind.

Wonderful analytics, albeit expensive to get the premium service. Word of caution though, their stats are not accurate representations of what's what. Its web traffic reporting only uses data collected from computers with the Alexa toolbar.

I use this website fairly often for work related tasks. They used to show a lot more backlinks, but now you can only see a few unless you sign up/pay. Eh.

This is probably one of the leading websites statistics aggregators out there which does not install any code on your site. I use this as a beginning stage of research about my particular sites or competitor sites but I still take it with a grain of salt.

I've looked at how they aggregate the data and it's not as accurate as you would like. They have to make a lot of compromises on the quality of the data and sample size because they are not all knowing.

The fact that it is backed by Amazon both reassures me in knowing that the quality might be good but also scares me in that Amazon gets to know so much data about the entire Internet.

Alexa collects and shows information about users who use its toolbar in browser. How many of you know about this toolbar and how many of you use it?