BrightEdge released a new report looking at social share metrics around Twitter engagement and the use of social plugins around the web. It draws upon the firm’s analysis of over 4 million tweets and 10,000 of the largest sites on the web.

According to the report, pages that show Twitter share buttons get 7 times the social media mentions than sites that don’t. A spokesperson points out that this points to an “enormous social marketing opportunity that brands can implement immediately at almost no cost.”

Another finding is that about half of the largest 10,000 sites don’t display any kind of social sharing link or buttons at all, which is quite surprising.

53.6% display some social links or buttons on their front pages, up from 52.8% in late July.

“It’s clear that social sharing buttons can drive real social traffic that will inevitably drive sales, brand awareness or even affinity but it’s also clear that many brands are not taking advantage of this simple, cost free tool,” said BrightEdge CEO Jim Yu. “It’s surprising that with so much talk about social and clear consumer adoption, almost half of the web’s largest sites don’t take advantage at all of free social sharing tools.”

If you need any more convincing about the power of a retweet, read about this bet from a poultry enthusiast.