LinkedIn has issued statistics showing that Holland at 38.2%, USA at 36%, and Ireland at 27% (in that order) has the hightest penetration of LinkedIn users per work-force capita. This is significant for business networkers, recruiters and job seekers. For example, if you want to recruit an IT professional in Ireland or a Sales professional for the UK, then LinkedIn now has the proof that these people DO exist there!
Brazil had the largest growth in penetration of LinkedIn users with 400% growth in 2010!