The problem with these "loopholes" is that the funding to subsidize the phone is coming from the carrier - in this case Verizon. Verizon pays Best Buy the commissions for the activation and the 2-year contract which includes the data plan. The commission paid to the retailer - Best Buy is derived from the 2-year contract and accompanying 2-year data plan. Early termination of either part of the plan would constitute the circumvention of being able to recover the subsidies by Verizon via the remaining portion of the 24 months under contract, and therefore suffer a net loss. This is why they have what is known as an ETF (Early Termination Fee). The ETF from Verizon is for the early termination of the phone plan, but the ETF typically charged by the retailer is to reimburse them for the commissions they would suffer the loss of once you terminate the data plan and Verizon takes back the commissions from the retailer.
There was another similar situation during the $0.01 phone sales that Amazon was running last year. They were losing the back-end revenue on the data plans because people were activating a new phone line onto their family plans with data, getting the phones for $0.01, and then pulling the data plan off the new activation, moving the phone to their unlimited lines and just paying the $10/month for the additional line. This was quickly squashed. I'm surprised that Best Buy has let this go on as long as it has.
This is the same way all third party retailers (Authorized Verizon Dealers, i.e. Amazon, Best Buy, Costco, Radio Shack, private Cellular dealerships, etc.), get paid for the activations and the subsidized reduced prices of the phones. This loophole WILL eventually be closed once someone at Best Buy figures out they've been losing their revenue source for the transactions being completed in this loophole, but like mentioned above, those who get in under the wire will likely be allowed to keep things the way they are. The talk that there is no ETF in the Best Buy agreement is hogwash. It's there, possibly under a catch-all phrase but it's almost certainly in there somewhere. Also, someone at Best Buy will likely lose their job for allowing this to go on as long as it has.