Aronald Kim, reporting for MacRumors:

However, according to training documents that MacRumors has received, Apple is not allowing any walk-in retail purchases for the Apple Watch at launch. Instead customers must make an online “Product Reservation” to hold a specific Apple Watch model at a retail store. […] Apple seems to expect low inventory for the Apple Watches, and notes that “try-on” appointments also do not reserve a specific Apple Watch for purchase. Apple expects to eventually allow walk-in purchases, but not until the initial wave of demand has passed.

I think this is a smart move on Apple’s part. There isn’t really a reason to encourage customers to line up for products anymore — they don’t need the additional press and the cult-like tone of waiting in line for a product is an easy target for mockery. Not to mention that waiting in line for several hours to spend hundreds of dollars on something you don’t truly need isn’t a great customer experience.