In countries that have not signed the
international treaty about intelectual properties
and such it's legal to produce and even distribute
this kind of stuff, however, those products always
become illegal by law once they leave that country
as they are not covered by international laws. I'm
not sure if china has signed that treaty or not
but Taiwan was the main example of a country that
doesn't (i say wasn't because i thought they were
going to sign it in about a matter of few years
and thus the companies that made those products
were being dismantled).....

Of course ebay and amazon know those things are
illegal (when talking about amazon i only refer to
the 3rd parties that they sponsor, not to the
items that they directly sell). However, there's
not much they can do to avoid it, they would have
to spend a lot of money and the results would not
be worth enough; After all, pirate dvds/cds or
whatever other media are like downloading mp3's
from internet, even with CD copy protection the
songs keep being ripped and spread through the
net, they cannot stop it so easily.

From my experience the best to do is to avoid
these kind of items, they may seem cheap but in
the end they end costing you more than the legal
stuff. In my old times when i didn't know a thing
about pirated stuff i got many cds and even dvds
from these sources just to realize that their
quality was so bad (bad subtitles, defective
discs, etc...) that i ended purchasing the legal
cds/dvds time later when i realized of my
mistake.... If i had known about the legal
releases i would have saved money.

It's sad to say this but nowadays the best way to
ensure that a dvd is legal on an auction is if
it's region coded (pirated dvds are region free).
I say sad because cd/dvd protections should be
illegal too in my opinion as they can make things
difficult to people who purchases them (if they
live in a different region code sector). Besides
this, another thing that you have to avoid on
online auctions are for dvds with both chinese and
english subtitles. I cannot tell for sure if there
are legal versions of these but all the ones i
have seen are pirated.