I think he makes very little sense to be honest. I have a Google+ account which I never use or post anything to because the majority of my friends are on Facebook. All the people I have added on Facebook I have met in real life and are real world friends either present or past (people I used to go to school with) and certainly all people I would like to meet up for a beer with again. I have maybe 150 people on my friends list, just don't be a douche and add every single person you ever meet in the street and you should be ok!

I have a LinkedIn and Twitter account, which are strictly used for professional purposes. No bitching, no moaning, very little swearing (if any). Separation of concerns. I think the fact that Facebook is a Social network would have given that away. I like the fact it is closed, I don't have followers and groups now allow me to target some of my posts. (The only thing FB is missing is Circles, that would allow me to truly separate out different groups of people).

a) it’s too easy to build: technologies or how easy something is to build plays no part in it's popularity, the end user really doesn't care and your average user doesn't know what that .php, .aspx or .js extension really actually means.

b) it has no (large scale) viable business model: It has a viable business model, possibly just not as large as the one the market has put on it, 2 different things in my opinion.

c) this is not what people want: clearly it is otherwise there wouldn't be a billion people using it. I want everything in one place, it's one of the reasons I visit HN, I don't want to go to several different specialist sites to keep up to date with my friends. It's also the same reason I don't use Google+, because I have 7 friends on there and even they hardly ever post anything. If I wanted somethinf very specialist then I would join a specialist forum. Only time I think this could be useful is when I am trying to meet new like minded people local to me - so I think your app nicely fills this gap.