From Mashable:
# 1. It’s more engaging.
# 2. Facebook is where the action is.
# 3. It’s free.
# 4. It’s a bigger network.
# 5. It’s more open.
# 6. The Like button.
# 7. It’s better for branding.
Source: http://mashable.com/2011/10/09/recruiters-prefer-facebook/