I think Yang is posting on BPL precisely because he cannot seem to work out the problem with SMD. That's what I would do if I was having an issue with a cottage manufacturer and they were no longer responding to me, since at least here the cottage manufacturer would have to pay attention and sort out the problem. In Yang's last post he said his last email was "a couple of weeks ago", which suggests that Yang waited quite a reasonable amount of time before taking the step to post here.
I'm not sure, but I think Yang doesn't live in the States, and so I think he has the extra trouble of dealing with a business that probably doesn't trust customers from abroad, especially from where I think Yang comes from. Yang might also not be a native English speaker (I'm just guessing... perhaps I'm wrong). How this translates to the attitudes at SMD I have no idea. But it could possibly be a factor. Over the years I've dealt with lots of American businesses that treated someone from outside the States with overly cautious or downright nasty reluctance. I'm not saying that SMD is like that, but who knows?
A lot of the responses in this thread are being pretty nasty themselves. In the same way that businesses ought to interact with courtesy to customers, I think showing courtesy to someone here in the forums, by assuming they are innocent before accusing them of doing something unsavory, is a basic starting point when talking to anyone. Some of you might have no problem with throwing away money and not caring that a business deal wasn't properly worked out, but I'm sure many of you would. What would you do in Yang's case? Why should he bear the brunt of the problem? And why is SMD's reputation more important than his?
How about we take the stance of some of the other posters here who are at least giving Yang the benefit of the doubt? The problem could be any number of things, both on SMD's part and on Yang's part. But we don't know. So why automatically take SMD's side? It's not easy to post in a public forum where you can be subjected to all the criticism that is already being shown here. Takes courage.