I'm lead to believe that if you're the type of person who would leave for that reason then Zappos doesn't want you as an employee.
It's about people who immediately discovered they don't want to work there - but can't leave after a month because they just paid an apartment deposit, or moving costs. These people are going to spend the next 3-6months looking for work while costing you money. That's who you desperately want to get rid of on day 1.
Most companies do exactly the opposite - they hire you in Nowheresville Nev but if you leave after a month you have a big chunk of location/training/recruitment expenses to pay back. These companies are actively forcing you to stay there - hating them - for 6/9 months while you job hunt. And they somehow think the rules boost 'retention'!