Thanks very much for comments. I know its a difficult issue and question to advise on. Probably even as a lawyer 
I’m kind of hoping to be able to make it short. Like maybe 10 lines. So very different from the typical policies made by most large companies. If I can get it to make sense and have any value in such short statement.
And thanks for your interesting example. With the icon and google analytics, you are getting more information than I get (I currently basically get none info about use or users of my extension, besides the statistics that Mozilla’s addon store provides). But if I ever implement the favorites related feature I talk about, I too will have connections to a webserver or webapplication I’m running or have access to. And even a Flickr identity of my users, I guess.
I’ll think a bit more about it, and welcome any further suggestions, ideas and inspiring examples anyone would have…