On some accounts I use my real name on-line (Google+/Facebook/Wikipedia/personal blog), others (Q&A/Gaming) I use an alias.

My question is: Security and privacy wise, what can people do with my real name? What are the dangers of using your real name on-line.

This is actually an interesting new field in infosec - reputation management.


Employers, Law Enforcement and other government agencies, legal professionals, the press, criminals and others with an interest in your reputation will be observing all online activity associated with your real name. 
These "interested parties" (snoops) are usually terrible at separating professional and personal life, so you could be made to suffer for unpopular opinions, political or religious convictions, associates or group affiliations they consider "unsavory", and any behavior that can be interpreted in the most uncharitable light. (Teachers have been forced to resign for drinking wine responsibly while vacationing in Europe. No, really.)
Conversely, you need an online presence, otherwise you will be made to suffer for a lack of things for the snoops to spy on - employers, especially (from Forbes): 



  Key takeaway for hiring employers: The Facebook page is the first
  interview; if you don’t like a person there, you probably won’t like
  working with them. The bad news for employers, though, who are hoping
  to take the Facebook shortcut: “So many more profiles are restricted
  in what the public can access,” says Kluemper.



You must carefully balance your public and private personas. Give as little information as possible in your public persona, and be mindful that unknown entities who may be antagonistic toward you will look to use whatever you put online against you. For instance - you announce you're going to visit relatives for the weekend! Robbers and vandals may take notice (from Ars Technica:)



  39-year-old Candace Landreth and 44-year-old Robert Landreth Jr.
  allegedly used Facebook to see which of their friends were out of
  town. If a post indicated a Facebook friend wasn't home, the two broke
  into that friend's house and liberated some of their belongings.



Social media companies such as Facebook and Google have proven to be hostile to the notion of privacy, and continually change their terms of service and "privacy settings" without consent to share more and more of your information with others. You cannot rely on them to protect your public reputation from your personal life. From NBC:



  The Internet search giant is changing its terms of service starting
  Nov. 11. Your reviews of restaurants, shops and products, as well as
  songs and other content bought on the Google Play store could show up
  in ads that are displayed to your friends, connections and the broader
  public when they search on Google.
  
  The company calls that feature "shared endorsements.''



It is best to offer information of a more personal nature pseudonymously, and keep the pseudonym(s) carefully firewalled from your real identity. Avoid major social media services when participating online pseudonymously if at all possible.

