The single biggest challenge is managing the constant, inevitable exceptions. Too many brands think of fulfillment as a machine you set up once, but the reality is that it's a process of continuous problem-solving. Your boxes will get damaged, carriers will lose packages, and shipments will be delayed. The real work isn't just picking and packing; it's managing the fallout when things go wrong.
Jay Sauceda made this point beautifully on Ecommerce Conversations when he said he considers his 3PL to be in the "exceptions management business." That's the perfect framing. Your success doesn't come from a magical system where nothing fails, but from having a robust process for fixing the failures quickly and communicating clearly with customers. This operational resilience is what separates amateur sellers from professional brands, especially as you scale operations and the number of potential failure points increases.
The critical nuance here is that customer expectations have completely changed the stakes. As Jeff Orschell noted on Retail Remix, fulfillment has become a key point of differentiation. Customers now expect fast and free shipping, and they have very little patience for errors. A decade ago, a shipping delay was an acceptable annoyance. Today, it's a reason for a customer to abandon your brand forever. This is the environment that Dhruv Saxena of ShipBob describes, where direct-to-consumer brands face when trying to manage their own fulfillment and compete with the standards set by giants like Amazon.