Really though, it seems near impossible to make a coin that could not be run over by throwing more resources at it.
That is the core of it.
Read up on "51% attack" also known as "50+ % attack".
First you need over half of the CPUs or GPUs or FPGAs securing your chain, or a specialised ASIC that can mine your chain (with other types of ASIC that were designed for other coins not being use-able for your chain.)
That is why it is only recently that Bitcoin started to look secure enough to potentially be able to maybe be secured.
By late 2014 hopefully enough bitcoin-mining ASICs will be deployed defending the Bitcoin blockchain that it might seem reasonable to hope that it should be reasonably unlikely that anyone will be able to mount a successful 51% aka 50+% attack against it.
Until then the sheer lack of security of the blockchain might well explain why Bitcoin's price has managed to keep getting crushed for so many years: it is just too easy to believe that it is still too vulnerable to be a secure store of wealth/value.
Blockchains are insanely, horribly expensive. If you don't have hundreds of millions, maybe billions, to devote to securing them they are simply too impractical for serious use.
You need to be massively higher in hashing power than all the general purpose hardware in the world, so that only special purpose hardware designed specifically for your blockchain can possibly hope to succeed in a 51% aka 50+% attack, and even then you have to worry about how easy it would be for some attacker to gain control of, or build/deploy, as much hashing power specialised to your chain as your chain's devoted defenders can.
-MarkM-