I have well documented the bike industry's battle against counterfeit product here on the blog. (Here and here specifically, with other references throughout.)
Aside from the obvious effect it has on manufacturer/distributor bottom lines and brand perception; counterfeit product presents a dangerous safety risk. Authentic products are tested to extreme levels of performance by the brand which designs and produces them to ensure they deliver on the promises they make but also to protect the end users - us - in this inherently dangerous sport we love.
Have you ever experienced a component failure? I know from my years behind a bike shop counter that those experiences are few. But; the ones I have seen are scary and often quite injurious to the user as well.
Counterfeit products can be hard to spot (except from the often accompanying "too good to be true" price); but the downside to the risk is huge. Learn to identify some of the warning signs that a product may not be what it is represented to be and be an advocate for your own safety.
Finally - buying authentic product is also a way of saying that you want these companies that produce the best gear in the world to stick around and continue doing what they do best - serve up two-wheeled joy! Buying fake goods puts money in the hands of cheaters instead of those doing the hard work as well as delivers an often inferior and unsafe product to you.
Zipp posted some photos on their Facebook page that are helpful - not only for their products - but as a guide for what to look for on many bands.