All 'non Web 2.0' (and 'non web') laws and regulations will also apply.

There may be some that are specific to your sector (e.g. financial), purpose (e.g. sales), rules of organisations you are a member of (e.g. professional associations, standards schemes, accredited standards), internal controls (policies and standards), type of data (health, employment, payment) and entity type (e.g. charity, company, local or national government).  Your location, user's location and web site terms and conditions will affect these as well.

But possibly two key ones are:

• Data Protection Act 1998
  
• The Consumer Protection from Unfair Trading Regulations 2008

If your audience includes children, there is also child protection legislation to consider.  So define:

• who will be publishing (and their legal status)
  
• who will be reading
• what level of risk you are willing to accept
• what controls (e.g. moderation, review) will be in place
• what data is being collected
• what purposes the information is to be used
• how long the data will be kept
• how the data will be destroyed when finished with

Then check with your legal advisors what legislation applies (and in which countries).  Some resources which may be of use:

• ICO For Organisations
• OfT Consumer Protection from Unfair Trading Regulations
• UK Data Retention Requirements

You might also want to read the e-consultancy forum reply Who is responsible for a forum content, do T's & C's cover damage to businesses?

Regards

Colin Watson
Technical Director
Watson Hall Ltd for website security