I think this responds to Facebook's continuous decline in service. They have messed up the algorithms so bad that News Feeds tend to be more static than ever before, back in the good days, people checked Facebook a hundred times a day because there was something new all the time. Today, if you check your Facebook 5 times during the day and you will probably get the same news as before.

They also pissed all their page owners off with Edge Rank, which was rolled out too aggressively for my taste. Since not every facebook page owner is a facebook or SMM genius, a lot of small pages lost a lot of engagement, which turns into less engagement on the site overall (from users and page admins).

I started using G+ a couple of months ago because of their Hangouts, but am gradually becoming more engaged on the site. Facebook will fall, and pretty soon I think. Too much spam, horrible filters and crappy customization on your share settings make it a shitty service now. As G+ emphasizes share settings control, I can see why it will take over pretty fast, they just need to gain a little more momentum.