Fran, That message Google is showing is a big concern to many people. But as a matter of fact, Google is using G+ as a major factor to send traffic to your articles(site).
Here is how it works:
Assume that you have 1000 people in your circle(friends in your Google plus a/c).
You like one of my article and click +1 to my article. When that article is shown on search engine result page(SERP) to people in your circle, along with the article link it will show that YOU liked(+1’ed) it. So people in your circle are more likely to visit and read that article.
This way, Google is using this social signal to bring more and more targetted and relavent things up in the search engine result page.
Now you have to decide whether or not to signup for Google Plus. For me: I don’t bother if they take my geographic location, web movement details secretly. So I’m already on Google Plus. And I also have a Technotip Fan page there.