Google+ has hit 25 million visitors

This rate of growth is much faster than that of Facebook, Twitter and

MySpace over the same time period.

Gmail penetration appears to be a key factor in Google+’s growth.

“20% market penetration is the tipping point for social networks — once they reach that level, they tend to become firmly established“

More info on Mashable http://on.mash.to/qvgv65