The big problem with GPU-mined coins is the number of GPUs controlled by people susceptible to memes.

Even litecoin's hashing-power was exceeded by some stupid meme out of the blue.

Luckily for litecoin, that particular meme happened to say "lets be yet another scamcoin!" instead of "lets trash all the scrypt blockchains!" but the next meme might not be so gentle...

-MarkM-