Google +1 is the latest social media tool from google, a direct translation of the Facebook 'like' button that has become so prolific. It allows users to mark a page as being, in the words of Google, “pretty cool”.
So why should you care? After all it is just another 'like' button. Well, aside from the obvious benefits to your exposure there are other factors that will help to increase it even more:
Google have stated that their search ranking calculations will include the +1's of friends (assuming you are signed in)
Google search results will list all of your friends that have +1'd a page (and what better recommendation can you get than that of a friend)
If none of your friends have +1'd a page, or you are not signed in, the search results will display an aggregate of the number of people that have +1'd that page.
Aside from the search engine optimisation (SEO) implications (which in my opinion are tempting enough) there's more. Google have included a callback that tells your website whenever someone +1's or un-+1's a page. This allows for anything from a simple display of thanks to a complete change of the user experience. It is important to note though that Google are fairly strict about how you can use this information. To quote the google policy page “Publishers should not promote prizes, monies, or monetary equivalents in exchange for +1 Button clicks.”, although they do allow you to 'unlock' content for users that have +1'd a page you will need to be careful that this isn't interpreted as a monetary equivalent (for instance if you charge users to download a document but allow it for free to people who have +1'd you, this could be taken as a monetary equivalent). You could also use this to catch whenever someone removes a +1 and display a simple text box, giving them the chance to explain what put them off and what could be done to improve the page.
If you do decide to use it then it is recommended that the +1 button is displayed in a prominent, logical place (next to the page title, above the fold, with all your other social buttons). An alternative option, that you could use in conjunction with the above, is to put a button at the start and end of every article. Google also recommend putting a button on your homepage to get brand endorsement (i.e. Fred +1'd www.mysite.com carries a bit more weight for your site as a whole than Fred +1'd www.mysite.com/products/a-category/my-super-product).
Google +1 also supports the “canonical” relationship declaration. This is a tag that can be included in a webpage to notify end users that this page is just an alternative version of another page and should be treated as such. This means that if you use canonical URLs then all your +1's will be aggregated into the defining URL for that content to prevent your +1's being spread over different formats.
Google +1 is more than just “another sharing tool”, it is also a search tailoring tool and, in my opinion, exemplifies the aims of the social-network-sharing idea with it's ability to influence your search results based on your friends opinions. I would say that for any website looking for more exposure, whether your a shop or an association, this is one of the must have share buttons.