Maidnet  +1   it's confusing, but Maidsafe is the company and The SAFE Network is the name of the network. but I'll use both Safenet and SAFE and whatever  .

Companies and forums use security walls when you try to get in. So passwords etc. Safenet works different, they say; "servers can't be safe, so let's secure the data instead of the servers". So chunks of data are encrypted and decrypted locally on your machine only. That's where the security comes from. So they don't have to hire big datacentre's, and security teams to protect against DDoS attacks etc. The networks uses P2P to spread all the data over the network and because it's all encrypted it's already safe. No DDoS possible as well. The only thing you could do is DDoS one or 2 nodes in the network but you don't have a clue where all these nodes that form groups are in XOR. So you can't target a node, a group of nodes or pieces of data.

They use "MIO" to speed up the nodes locally so nodes can handle over 60.000 messages a second. So extra encyption layers and all these messages that are crypto signed shouldn't be a problem when it comes to speed. But we'll have to see what happens when we have a couple of thousand Vaults at peoples homes.

Yes, you can download for free, that's the idea. Maybe they make a change to that, but they want people to use Safenet, that's why. And when you pay some Safecoin to store a file, you are not paying to the ones that's storing the chunks. You actually "burn" Safecoin so the addresses of the safecoin become free again. People that deliver data to the network get payed when they deliver a chunk from their Vault and the random Safecoin address that's picked by the close nodes  is free. So safecoins are recycled in a way. And when a file becomes populair nodes will deliver it from cache instead from a Vault so nobody makes money on it. All nodes in the network cache up to an x-number of chunks that come by. So when you request a chunk, and it's 5 HOPS away, the Vault makes money once. But because these 5 HOPS have cached that chunk now, when you request it again, or somebody close to you, it's delivered from cache from one of these HOPS. So data becomes faster when more people download it. And as a Vault you don't win the lottery when you have a very populair chunk  .
 
Here are some videos about the technical details:

1.1. What is the SAFE Network?
1.2. XOR Distance and Basic Routing
2.1. Recapitulation of Lecture 1
2.2. Visualizing the global connection patterns in XOR Space
2.3. How do the Overlay (XOR) Network and the Physical Network relate to one another?

Video about Safecoin:

The Economics of Safecoin