Can You Have Privacy on Facebook and Twitter??

I just read some articles about several privacy issues and internet security concerns about web2.0 sites Facebook and Twitter. In the article Can You Have Privacy On Facebook? The author lists 2 issues by now . First,

Facebook Publishes User Information Gathered from 3rd Party

In November 2007, Facebook launched Beacon, a system where third-party websites can include a script by Facebook on their sites, and use it to send information about the actions of Facebook users on their site to Facebook, prompting serious privacy concerns. Information such as purchases made and games played are published in the user’s news feed. Originally if no action was taken, the information was automatically published. On November 29 this was changed to require confirmation from the user before publishing each story gathered by Beacon.
Second, Facebook Source Code Leaked Onto Internet
Then there is the Twitter private message leaking issue which were found last year.
Privacy and Security Concerns Rise After Twitter’s Privacy Disaster Everyone who uses Facebook and Twitter should read this 2 articles.