E-consultancy reports a survey from Clearswift about staff use of web 2.0 sites presenting a potential security risk for businesses.
The survey findings are well presented, showing a picture of increasing use of social media sites during work hours by younger employees:

The survey highlights the considerable amount of time today’s young office workers spend surfing social media sites from office PCs, with 39 per cent of office workers aged 18-29 admitting to accessing social media sites ‘several times a day.

It’s particularly heartening to see the conclusion reached by Clearswift’s Ian Bowles:

Finding the balance between harnessing so-called ‘Web 2.0’ technologies for business benefit and maintaining strong security is key. For example, it isn’t difficult to envisage an employee posting unauthorised comments about their organisation’s product or service quality issues on a blog – causing major brand damage – but at the same time, banning all blog access is not the answer as it cuts the organisation off from conversations with partners and customers.

The point for me here is that web 2.0 tools don’t present any more of security risk than existing business tools such as email. Tools don’t leak sensitive information, people do.
The real focus for keeping sensitive information private needs to be on people – a mix of policies, organisational culture and management to minimise the risk of information being leaked, regardless of the tools used in the organisation.