Most social media monitoring systems measure topics, sites, products or services rather than people.

FORBES: Can You Measure Your Digital Eminence?

Recent reports about the Department of Homeland Security and the FBI monitoring sites like Facebook and Twitter raised many a public outcry about the social media version of Big Brother.

FORBES: Why It's Not Completely Ridiculous For A High School To Monitor Students' Tweets

The Syrian Media Centre, a private monitoring organisation, told Reuters in May that the Syrian authorities blocked 225 internet sites in 2008, up from 159 in 2007.

ECONOMIST: A silent social revolution