Wouldn't be the first bad spending decision our government made.
Seriously, ps3's? At this point, video cards give better performance per dollar with OpenCL or CUDA, and PCs are able to support more than 256MB of system memory and can have wicked fast network connections between them. Building a super computer out of ps3's just seems naive.
So the PS3, at a cost of $300 per system, delivers 150GFlops (single precision, only around 10GFlops in double precision...they'd be complete idiots to be using ps3 cell for double precision), 256MB system ram (the gpu is not accessible in linux), and a single gigabit ethernet connection.
A $110 4770 can do 960Gflops single precision, and 192GFlops in double precision, with a fair amount of money left to buy the rest of the system, which will most likely have more than 256MB ram, won't have a blu-ray drive, and could have additional gigabit ethernet ports.