If Diaspora fails, it will have less to do with the awesomeness of the project, and more to do with the lack of everyone's friends actually using Diaspora.
I figure it will be a huge hit among geeks like us, but then will fall out of usage due to the lack of updates from people that matter, like friends and family.
I use Facebook for staying in touch with the mostly non-technical people in my life who actually use Facebook, and that's what will end up swaying most users (like myself) back towards Facebook in a relatively short period of time.
Non techie friends and family pay a lot of attention to what techie guy does. I remember using google when everyone else was using yahoo, and soon all my friends and family started to use google over yahoo. In 2006, I switched to mac. Half my non-techie friends and family now have macs. Trends, possibly, but they'll try it if they know you like it and if it is better, they are sold.
In the cases you mentioned, it was easy for the techie guy to recommend Google or Macs to friends or family because they were far better products at the time.
I take recommendations I give to people very seriously, and I simply wouldn't recommend to any non-technical person to move away from Facebook to a platform that has none/few of their friends on it.
I figure it will be a huge hit among geeks like us, but then will fall out of usage due to the lack of updates from people that matter, like friends and family.
I use Facebook for staying in touch with the mostly non-technical people in my life who actually use Facebook, and that's what will end up swaying most users (like myself) back towards Facebook in a relatively short period of time.