I think that crypto is a special case of the problem MaidSafe is solving, which is storing mutable files. Token ownership is just a special case of file access. You can either replace the content of the file (as with safecoin) or append to it (as with ever-growing histories).
Also I would say that Vitalik’s criticism here isn’t of the Maidsafe consensus algorithm, but rather of the section size in Kademlia. He wonders whether such a small number of computers can be enough to prevent double-spending when money is on the line. A few things need to be pointed out:
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The amount of value in transactions that can be reversed by double-spending is proportional to how many sections you can compromise. However, this by itself is not enough as a virus or sybil attack can cause a serious problem, that can lie in wait for a year and then destroy the network.
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The actual math shows that the probability approaches zero fairly quickly even with a small number of computers provided that only a small proportion is compromised
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The consensus algorithm matters a lot.
At the Intercoin project we developed innovations to be resilient to 33% malicious nodes, which you might want to take a look at over here. What’s interesting is that our consensus mechanism also got criticized by Ripple’s chief cryptographer on our forums, but he admitted at least that it actually works and did not point out any security problems with it. So it might be useful for MaidSAFE to adopt some of those ideas!