Twitter Counter is a tool for Twitter users to analyze their followers. I enjoy using it because it’s simple, straight to the information, and effective in empowering me to see my historical data. This is obviously focused on the followers model, but can be applied elsewhere as well. You can upgrade this tool (as you can all the ones mentioned) to include extra analytics features.
One piece I found interesting is the ability to buy your own Twitter followers. Not dissimilar to real world activities, you can give money to the company to boost your following. As they say, “You pay for the number of pageviews you want to be promoted. Your profile will be visible on the Twitter Counter homepage, the sidebar and on the top 100 user list. Additionally, you will be featured on the homepage of our sister site Twitaholic.com.”
As for the premium data analytics product, listed here, http://twittercounter.com/pages/premium, there are multiple tiers to the upsell. The primary difference is the number of users that can use the premium version.