Netflix has become extremely popular since its inception, using the existing mail system to create a relatively efficient and easy to use movie rental empire. While their subscribers might enjoy the relative ease of picking up movies in a mailbox and returning them the same way, the US Postal Service is less than pleased. It seems that the very design of the envelopes causes problems with the mail system, enough so that the USPS claims they have spent an additional $41.9 million over two years in processing these.
The issue stems from the shape and design of the envelopes, which prevents them from being machine-handled. Obviously with the enormous amount of mail that is processed, having machines doing a lot of work is necessary. Perhaps when Netflix was small, this wasn't an issue - but now, with their size, it is. USPS is demanding that Netflix change their design or face a fee for every envelope they send.
It seems Netflix will comply with the USPS, and has decided to go for a redesign.