

Networking sites make it easy to publish current CVs and other data of great value to identity theives. If it is on the Internet, the data can be found.
Search for a person's name and the probaility is that the more they are in the public eye, the more chance that a search engine will find them on a networking site. Past and present directorships, senior positions and club memberships: all easy to find. Published Annual Accounts reveal your public income.
Most networks offer public and private settings. If your friends are allowed access to your private contact details, that information is only as secure as the security on their computer. If they are infected with malware, your data can be harvested.