You can read all about it on the news page
The full text of the lawsuit is posted in the Downloads section of the knowledgebase.
Here are just some of the reasons Profile Technology had to sue Facebook:
1. Facebook has been impersonating Profile Technology Ltd and Profile Engine and spreading misinformation to the general public about Profile Engine, including through a fake Facebook page in the name of Profile Engine which they refused to remove.
2. Facebook has breached a 2007 contract allowing Profile Engine to freely index public information from Facebook without any limitation.
3. Facebook has breached a contractual obligation to keep the information they provided to Profile Engine up to date.
4. Facebook has published false and defamatory claims about Profile Engine and Profile Technology Ltd.
5. Facebook has caused the users of Profile Engine serious inconvenience by deliberately making it very difficult for them to log in and claim their profiles.
6. Facebook has caused the users of Profile Technology's many popular Facebook applications (and ourselves) huge losses by denying those users access to their applications, including applications they had already paid for using Facebook credits.
7. Facebook has censored the free speech of Facebook users, preventing them from discussing Profile Engine or recommending profileengine.com to their friends.
For the full details of the lawsuit please download and read the PDF document from the Downloads section.