I use G+ because I don't use Facebook; I think I was rebelling against the popular shift, and then I started hearing about all the privacy problems. G+ is practically foisted on you if you have a GMail account, and many of my friends went to G+ so it worked out. There's also Google Hangouts, which work really well and have enabled me to be much closer to friends who live in other states and time zones.

People get mad when others disagree with them because it's human nature to not only take your own opinions for granted, but to perceive disagreement as a personal attack. Some are more sensitive to this than others, and most of us are more sensitive to particular opinions than others. There's a reason why the Freemasons have a rule to never speak of religion or politics at their meetings.

The specificity of when umbrage is perceived can even be narrower than the topic itself. If Joe blogs that he just bought a new Toyota pickup truck, and one of Joe's friends made the comment "You should'a got a Ford, Toyotas are crap" then it probably won't lead to any hostility: they can still share a beer. However, if you took the same people and this time Joe blogs that he just bought a Chevy pickup, and his friend said "You should'a got a Ford, Chevys are crap" then it can turn into a very bitter argument with lots of resentment, because in some places there is a very specific relationship between Ford and Chevy pickups that doesn't extend to other brands.

Or picture it as someone announcing their new boyfriend. In one case the woman's friend congratulates her, and in another case she might launch into a vicious tirade. The difference? In the second case the new boyfriend was someone the other woman fancied as well.

Posting this kind of thing publicly can make it worse, because now you add the need to maintain face in front of both friends and strangers, so the participants put more energy into it and quickly take their emotional investment too far.