There's an interesting debate happening on LinkedIn relating to an application which automatically brings up details from the Facebook profile of a candidate when they email their application. As one recruiter points out, "Alongside the CV you've lovingly crafted and mailed over they could see a side you didn't intend to share. The one of you gurning on a stag weekend…"
Recruiters need to be very careful using such tools. It's pretty much accepted practice that recruiters will seek background checks on candidates. But this foray into personal areas isn't without risk to the recruiter. And it's an area that's highly regulated by law.
The Data Protection Act requires that all information gathered about an individual is relevant to the purpose it's needed for. It'd be difficult for any recruiter to argue that photos of a private family event outside of work hours are relevant to a work application.
Public sector workers have even more protection in the form of the Human Rights Act which protects them from Government intervention into their private and family lives.
I can see the potential for a lot of legal action when candidates find out their Facebook profile was accessed and they were turned down for a role. Imagine a mum to be announcing she's pregnant on Facebook, or photos revealing that a candidate is in a same sex relationship. There's more than enough room for a determined lawyer to sue for discrimination. Is that really what you want to get your client into?
Unless a private life has the ability to impact on a professional life then the two should be left apart, especially in a recruitment process.