China (The People's Republic of China; Mainland China; "Communism with Chinese Characteristics;" the CCP etc) is a different place to Taiwan (The Republic of China; Formosa; Asian Tiger economy, etc.).

If you have bought a carbon bike or frame from a major company, chances are it was made in Taiwan by a company like Giant. Giant has been really innovative over the years and lead the way with making carbon frame technology widely available to consumers. They also have a generous carbon frame replacement offer and coverage for manufacturing defects. In general, carbon frames made in Taiwan have the carbon fibers carefully laid by hand in molds--it's one of the most highly paid jobs in the Giant factory and often performed by very skilled women--to achieve optimal strength and frame safety. I trust carbon products made in Taiwan as I have ridden them for years without mishap.

The carbon frames OP is talking about are the ones you see on eBay, Aliexpress and Alibaba. They're made in Mainland China and lack all or almost all of the features that make Taiwanese carbon frames reliable. The carbon fibers often aren't laid carefully, and their orientation, based on frame axis, etc, may be off. The vacuum machines for removing all air bubbles from the resin are not as good in some cases and can potentially leave voids within the frame, creating weak spots. Those frames also used to break down under UV light exposure and were weak around the junction of the head tube and the downtube in some cases, leading to failures where the front wheel "dived" under the downtube. There is a small but often vocal minority of Chinese carbon frame defenders who will say that all of the above points are either exaggerated or have been solved, and it may be somewhat accurate, but on the whole, they just can't be trusted. The whole "think light, cheap and durable, now choose two" comes into play, as they're cheap and light. I just don't trust carbon products from Mainland China.