Facebook & Twitter are the giant lords in the world of Social Networking. These sites effects the Search results extremely, facebook does it by likes and shares, and the twitter does by tweets from original user accounts.
Google plus is not at all popular in respect to Facebook or Twitter. So, in order to catch the market Google have taken this strategy that any user or site having google plus page will have better ranking in the search results. Although, the google executives are not saying this clearly, they are only saying this 'any user having better social profile will have better search ranking'. This is confirmed that Google plus profile helps to rank better. In an experiment Rand Fishkin of moz.com(previously seomoz.org) have confirmed it.

Which method of link building do you prefer, the conventional guest blogging process or other link building techniques such as blog commenting, article submission, forum posting etc ??

I ask my readers which Search engine will they prefer to have a better conversion rate in your sites ??