There are several things you can look at when measuring the success (or not) of your SMO marketing efforts; and of course it depends on what your overall marketing goals are, here are some others to consider besides the common metric options such as views, qualified visitors, increased sales and increased brand awareness:
Contributing content – assuming you have a blog and allow for comments; a quick and easy metric would be to monitor the number of visitors who are actually interacting (posting comments) on your blog.
Reading content – if you have a blog, a good way to measure engagement is to monitor who is reading your blog and where they are coming from. You can run web analytic reports that will show you what is the most popular content on your site (blog); how long they were on that page, where they came from, and also the bounce rate (percent of visitors who left your site after visiting a particular page).
Subscribing to a RSS feed – you can also measure how many web visitors are subscribing to your RSS feeds.
Who is bookmarking your site/blog posts – there are a couple of ways you can look at this metric. You can use your web analytic tool and run a click map report and see how many web visitors are clicking on the social bookmarking icons. Or, you can simply create profiles in each of the bookmarking sites and search for your urls. This can be very time consuming and would only recommend spending time searching in digg, del.icio.us, stumbleupon and netscape.
Emailing posts – assuming you allow for your blog postings to be emailed to others (see below); you can use your blog platform tool like wordpress to see how many emails are actually being sent through your web form.
Who is talking about you – another metric you can use is to see who is actually linking to your blog and talking about your blog postings. You can do this a couple of different ways; through technorati or searching in Google and Yahoo for the following: link:http://wangzhuan0811.blogspot.com. Or, if you have budget, you can hire companies like Radian6 or Collective Intellect, that offer real-time social media monitoring and analysis.
Final thought: to judge if your social media optimization succeeds or not, measure at each stage of your process is the key to identify where the fail points are.