A couple friends and I do this, but I’m sad that it wasn’t my idea and that it took us so long to do as a collective.
We share our Google Analytics data with each other for our various blogs and websites.
It’s been so far a great way for us to dive into different sets of data and look at how each of our sites, with different themes and audiences attract different users, that behave differently, and grow the possibilities for us to see something insightful where we can then we can actually recommend something to do.
Most of the time though, it’s just the finding of neat things out about your friends sites (sites that they put so much time into over the years that they run them). It’s neat to see which of your friends articles generated a lot of traffic, because you were there with them as they asked you for feedback on those ideas and they shared the links out when they finally published.
If you have a bunch of friends with websites, blogs, tumblrs, posterous pages, try sharing the analytics data for those sites with them. It’s a great learning source, and just a fun topic of discussion.