SEO Platform BrightEdge is reporting that its analysis of the Web’s 10,000 largest websites is showing a 33 percent increase in placement of the Google +1 button in the last few weeks.

While Facebook still claims a two-to-one lead in placement on these sites over other social networks, most brands are still not linking to Facebook. BrightEdge’s SocialShare Site Analysis found that 47 percent of sites are linking to the social network with Twitter seen on 42 percent of the sites measured. It is important to note that these percentages are based on the sites “linking” to Facebook and do not include actual social plugins.

When it comes to social plugins however, Facebook still leads the way with almost 20 percent of the sites including the plugin tools offered by Facebook. But Google+ is surging, achieving placement on 4.4 percent of the sites (Plugins from Twitter are displayed on just 3.4 percent of the front pages.

“Overall, this inaugural version of our SocialShare Site Analysis shows huge opportunity for brands to engage more socially,” said Jim Yu, CEO of BrightEdge. “Fewer than half the largest sites on the Web offer any kind of social link at all on their front page and these sites represent a massive slice of Internet traffic on any given day. We would expect to see a land grab effort this year as plugins vie for placement on this very valuable Web real estate.”