With about 25% of basket abandonment caused by a forced registration processes, customer account registration should simply be a function of the checking out process. And those retailers that make account registration and customer account login as easy as possible see significant uplifts in conversion rates later.
Burberry.com is a great example of a retailer that has done it right. Simply input your email and they will decide whether you are a returning customer. And if you are a new customer, you simply start checking out.
This focuses the customer on moving forwards towards checking out rather than becoming distracted or frustrated by having to remember or reset passwords.