I work in bike industry (retail) in the workshop environment and do a lot of
warranty / crash replacement - mainly for customers with carbon fibre road
bikes and less for mountain bikes
today I had 3 road bikes come into my workshop, all carbon, all with "issues"
(i.e. cracks) relating to the frame or forks, 2 were not warranty related
(both crashed), the other 1 was a valid warranty despite being 8 years old and
ridden very hard.
I've dealt with 100's of warranties and crash replacements on aluminium and
carbon bikes for some years; the genuine warranty jobs tend to be
manufacturing (QC) issues or structural (design flaw) issues. You will see the
same issues time and time again on the same model of frame and it becomes well
known among people dealing with these claims.
A common design issue causing repeated warranty claims on some specific models
was galvanic corrosion between aluminium alloy hardpoints (BB shell, head tube
cups) embedded in the carbon structure.
Personally I ride a carbon road bike, and carbon fibre hardtail mountain bike.
My CF mountain bike was a warranty replacement for an aluminium alloy hardtail
that had a manufacturing defect, they upgraded me to CF as a goodwill gesture.
Since then, I have had another warranty replacement of the same carbon fibre
frame due to an "known" structural issue with my current frame.
The manufacturer has stood behind their product 100% and their 2014 frame has
been redesigned, I know once my current frame develops the known issue I will
be moved onto the new model. I have no qualms riding carbon fibre frames.
If I had spare cash? I would definitely ride carbon wheels on my mountain
bike, but probably not on my road bike as I do a lot of commuting miles in bad
weather (350km / week) and prefer "hand built" wheels with common Mavic Open
Pro alloy rims.