I agree with a lot of what J.T.D. said. The whole issue of cheap, kockoff's is a lot more complicated than it seems. It seems to me that there are really 3 or 4 different catagories being lumped into one broad topic.
For example, there are cheap, original rc's being made. That's not a bad thing because every rc company started somewhere and some of those new brands could morph into the next Traxxas, HPI, Associated, etc. The bad thing is when parts break they can be very hard to get and that leads to a poor reputation.
Then there are the liscensed reproductions being made. The good part of that is parts from the original will fit and can be more easily found.
Then, IMHO, the worst are the unliscensed reproductions that are poor copies of good vehicles. This is bad on a bunch of levels. First, the intelectual property of a legit company has been stolen. Second, these copies usually use inferior materials. Third, many of these inferior copies are made to such poor tollerances/standards that replacement parts from the "original" will not fit.

So, in keeping with the helpful intent of the topic, I'd say that:
Cheap is not always bad.
Do a lot of research before buying any rc but especially the cheap ones
and
If you want to minimize the chances of problems, buy a well known brand