welcome to the forum 
People here on the forum who have āMaidsafeā behind their names are the actual Devs. Itās a team of 9 Devs and other that work for Maidsafe. Totally around 15 people I think.
No blocks are used. So when the network goes live and it works like expected it should scale to 1 million users without a problem.
Well, yes and no. Every file is like stored on 4 different places on the network. When a file becomes populair it will become faster due to caching.
Hereās Safenet in 5 minutes. I hope that explains some more. And below that it the Wiki.
https://www.reddit.com/r/safenet/comments/3qyqme/safenet_in_5_minutes/