i've had my fake 4gb for over a year and i never had any problems.
there is nothing different from the fake ones and real one apart from the loading/transfer speed, real ones transfer a lot faster but why complain, fake ones are a heck of a lot cheaper.
when i first got my psp i paid £70 ($140) for a real 1gb scandisk then 6 months later bought a fake sony 4gb for £30 ($60)