After sitting with the questions I inventoried in Learning new questions socially, and pondering the comments on that post, I've made some sense of Facebook. This is "subject to change with notice" and open to your ideas for revisions.
It's who you know: For us bloggers experiencing "professional development on steroids" (from writing, subscribing, quoting and reading blogs) it's WHAT we know that counts. Our particular content is valuable to each other. Facebook plays by different rules: It's WHO you know, HOW you know them and HOW they will make you look good -- that counts.
We've already met: Facebook appears to be designed for maintaining previous acquaintances. It works great for people who took the same class, stayed in the same dorm, went on the same trip, graduated with the same major, worked at the same employer, dated in the same circle, etc.
The more the merrier: Facebook creates a network for the mutual monitoring of friends. The more friends you watch, the more that can watch you. The bigger the web of interconnections, the more network effects that can kick in. Someone who doesn't know you will have heard of you, know what you do, considered that recent change you made, thought of you when something else came up, etc.
Protecting your brand: Facebook accelerates the formation of a personal brand. Reputations are created by what comes through each friend's newsfeed for others to read. Making good impressions depends on choosing your friends wisely. Subscribers are careful to not friend their parents or "the sexy trash" they are dating because all that uncool news would come through their feed where their other Facebook friends could read it.
Viral adoption of changes: One friend's change of embedded API's goes into his/her newsfeed. Other friends will see the change and consider doing the same. Their friends will see the newsfeed of that change. Change is Made To Stick and prone to catch on like wildfire. Many entrepreneurs see huge revenue potential in this.
Cashing in on college: Most alumni report being satisfied with their college experience. They see themselves as more mature, articulate, clear minded and confident. They credit the people they met and the activities outside of class. Most college graduates see their classes, homework and tests as useless. All this fuels the meme that the main benefit of college is "who you meet".
Making connections only pays off only if we stay in touch. Going our separate ways undermines the main benefit of that huge tuition bill. Facebook changes that by creating newsfeeds of friends. Staying in touch is ongoing and easily done. The chances of the deep debt paying off is much improved.