The way MaidSafe's economic model appears to work is we had an IPO where we bought Safecoins which are credit tokens. These tokens were a presale of Proof of Resource allocation.
Proof of Resource for storage space would be a situation where the farmer gives a certain amount of storage space to the network and they would be paid in Safecoins from people who don't have any storage space to give. People who don't have Safecoins will have to give to receive and by reciprocity they would have double the storage space (I think this is how it's supposed to work).
If you have Safecoins then you likely have a lifetime supply of storage space. Everyone else will have to provide storage space to the network in order to receive storage space. As a result these Safecoins will become the main way that people buy storage space.
Here is the quote from the whitepaper to back up what I'm saying
https://github.com/maidsafe/Whitepapers/blob/master/Project-Safe.md5. Economic System With Two Types Of Token
P.O.R is proposed in order to facilitate the exchange of storage space on the SAFE network. However, as it doesn't have a predictable cap number, it may not be considered a genuine virtual currency. To provide a more robust form of exchange, MaidSafe proposes a token system that is totally independent of P.O.R, called safecoin. Safecoin will have a predicatable cap and will be injected into network using the storage space related mining procedure.
A bridge (converting rate) between P.O.R and safecoin can be established by the market solely. With third party upper layer broker applications, it will be possible to use safecoin to buy P.O.R or vice versa (user_A gives safecoin to user_B in exchange for user_B's P.O.R). It is expected that the per unit value of P.O.R will keep decreasing, while the per unit value of safecoin will continue to rise. In this way, it will be possible to buy more and more P.O.R with one safecoin. Safecoin will only be stored in the Maid Account wallet, this can only be updated by the Maid Manager group.
The value one safecoin represents will be recognised by all peers across the network and outside the network. If the economic system works as intended, safecoin will become a ‘virtual currency’ with the SAFE network being used to complete all transactions. Meanwhile, P.O.R will solely be used for exchanging space allowance among users.
Storage space is usually deflationary. Every year we can expect storage space to decrease. Safecoins are capped at 4.3 billion but unfortunately these Safecoins are not divisible. The fact that they are not divisible could be a problem and I'm not sure why it had to be designed like that but I'm guessing because it's designed to exist exclusively within MaidSafe and to track Proof of Resource.
As resources become cheaper 1 Safecoin should be able to buy more resources. That means the buying power of 1 Safecoin should increase with Moore's law and the deflationary spiral of storage space. If these premises hold then Safecoin are like indivisible shares in the resources of MaidSafe itself. Since demand for resources are insatiable, the MaidSafe model will definitely catch on and make many billions of dollars.
There are ways to improve their economic model and the crowd sale was terribly botched. Too many Safecoins are concentrated into the hands of too few, but that is generally what happens.
It's questionable whether or not Safecoins need to be mined but considering how many devices there are in the world you would need at least 1 Safecoin for every device so having around 4 billion does make sense when there are around 3 billion devices. Whether or not people get their ROI depends entirely on whether or not MaidSafe is in demand and really I cannot see how it wouldn't be.
VPNs, MegaUpload/Dropbox, VPS, Amazon, Google, Facebook, even forums such as these would all be able to run on top of MaidSafe as an app. These large corporations if they are somewhat smart would start buying Safecoins so they don't have to buy them later but knowing how they reacted to Bitcoin and other disruptive peer to peer technologies we can expect them to make fun of it or demonize it early on. We can also expect a lot of file sharing to move there and probably be the first killer apps.