Google+ (aka Google Plus, G+) is a multilingual social networking service launched in June 2011. The Google-run social network allows for collaboration, status updates and segmentation of contact via Circles (as in social circles, similar to Facebook's lists). Google has described Google+ as a "social layer" consisting of not just a single site, but rather an overarching "layer" which covers many of its online properties. Other key features of Google+ include Hangouts (group video chatting), Events, Chat, Photos and the latest addition, Communities. Definition in part from Wikipedia, CrunchBase, SDLSM2.com
Positive Points:
Free to sign up and use - many already have a relationship with at least one Google property (typically Gmail)
Self-identification -- users choose to follow their favorite people and organizations, voluntarily identifying themselves as fans, in the same way having a shopping club card identifies them as fans
As an integrated part of the Google family of properties, Google+ profiles/pages and activity works to improve search engine (Google) visibility and ranking
'Targeted sharing' - users can control who sees what with each piece of content shared on the network
Potential Pitfalls:
As the relative new-comer in the social network arena, Google+ is playing catch-up to more established networks like Facebook in terms of user numbers
Behind every Google+ page is a human, and mistakes can happen; individuals and organizations can find themselves in the crosshairs for posting something others view as 'questionable'
Prevailing sentiment that Google+ is an inferior service, some resistance to adoption and continued use
User base currently skewing younger (student is the number one occupation), toward those in tech-based fields and male (66%)
Non-mobile users spend an average of 3 minutes/month on Google+