The point is: are they right? Is 51% attack so cheap? Litecoin's hashrate have pumped up significantly last few hours due to Solidcoin's so-called "economic change". If 51% attack is indeed so easy and cheap, it is very hard to trust Litecoin...
The dangers of CPU based chains. Renting CPU is very very very cheap. There is no cost effective method of renting GPUs. In an attack you don't need hardware over the course of years you just need it over the course of a dozen blocks or so. Renting gives you a huge multiplier.
Instead of buying 1 CPU and running it for a year. You can rent 300 CPU for an hour at the same price. That muliplier effect is what makes CPU based chains vulnerable and likely futile in the long run.
The only way I see "cpu chain" working is a blockchain which has the option of using one of two algorithms. They algorithms are selected to provide roughly comparable benefit on CPU or GPU. Even that may be not worth the complexity but a straight "GPU-hostile" chain is critically flawed in my opinon. It is the specalized hardware (GPU) that have pushed Bitcoin out of the reach of "cheap" 51% attacks.
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