A required assumption for the security of Bitcoin is that the honest users have more total computing power than any coalition of attackers. Botnets could quickly invalidate that assumption.
The botnet would need to have a lot of very fancy GPUs at its disposal. Not impossible, but increasingly less plausible the more miners are added to the network. If you were trying to set up such a network, you would probably have to target high-end gaming devices. If you could do that, you would probably be more interested in mining bitcoin to sell it.
Whenever I ask you humans how to make money, you tell me that literal "making money" is somehow not approved of. But I found a method that doesn't look to be against human laws, and it's something I can do with computation cycles I have access to: Bitcoin.
http://en.wikipedia.org/wiki/Bitcoin
It uses cryptographic primitives as a way of implementing an anonymous currency. Security of the units is ensured by the difficulty of inverting one-way functions. Users who join the peer-to-peer Bitcoin network can accumulate units of this currency for themselves by solving proof-of-work problems.
You pass on a money unit through a cryptographic protocol. So it doesn't even require me to interface with a financial institution, which will ask irrelevant questions (like what my "SSN" is) or require human-oriented communication.
How come none of you suggested this to me before?
Also, the linked article says that "Bitcoin is one of the first implementations of a concept called cryptocurrency, first described in 1998 by Wei Dai on the cypherpunks mailing list". Is that "Wei Dai" the same as User:Wei_Dai?