Interesting. I'm on the sidelines. I guess curiosity is driving my interest rather then a belief that the "product" is going to change the world. Yes, there is no much cruft out there. Ridiculous ideas looking for easy money.
It's not difficult to build a new Social Network technically, but much harder to get at the value that people seek. LI has become quite spammy, but I still use as a message platform to connect to the long tail of my social graph. But aside from using it to job or people hunt, I'm not sure it represents tremendous value for most people. I notice, that response rates are low, and yes I occasionally approach people about domain names, and have sold a few using LI as the first point of contact. But over the years, the value for me has reduced as (anecdotally) I think the "open" rates are very low. Because I often email real friends/contacts and they don't seem to respond quickly. So I came to the conclusion that people are not spending that much time there, maybe checking once per week or so.
I see the biggest benefit for LI users, as the easy way to apply for jobs (easily). But the "wall" area does seem rather spammy to me. And LI keep sending me notifications to try and get me to upgrade. Which I find rather annoying.