China Daily ran a story about customs seizing about 37,000 fake products in the out-bound mail--seven times the amount seized in 2008. From the article, it sounds like all of incidents were through China Post and not through international shipping companies (though that detail is left out).
It sounds like the post office isn't doing its job. From my experience in the post offices around China, they check every parcel before it gets sealed and stamped, which can cause a person to wait a long time to send something as simple as a postcard. And they do have some rules for international mail, as my wife and I discovered.
Jia wanted to send a small package to my parents after our wedding. Part of the package was a DVD of our reception. Unfortunately, the videographer used a DVD label that had pictures of Mickey Mouse--a blatant infringement of intellectual property. China Post wouldn't allow Jia to send the DVD because it would get seized by customs--she later took it to a Kodak store and had them write it to a blank DVD without a label.
We also had a similar experience when shipping a few boxes of our belongings via DHL before we moved to the US (see previous post).