Posts from Best Buy's community forums - http://forums.bestbuy.com/t5/Mobile-Phones-Mobile-Broadband/... - suggest that buying phones online subject them to an "Equipment Discount Provision" - http://wireless.bestbuy.com/template/simplecontent.aspx?page... - which enables Best Buy to recover the difference between the discounted price and the full purchased price if you cancel your phone contract within 180 days. If this is the case, you would end up paying both T-Mobile's ETF and Best Buy's fee, making your contract-liberated Nexus S $200 more expensive than just buying it without a contract.
