I think you're overstating the relationship (unless you're one of the execs ).
No, I'm just a customer. I don't understand the "overstating the relationship" part of your comment. Virgin Mobile USA, Inc. is a wholly owned subsidiary of Sprint Nextel Corporation. You can't over or understate something like that. It's just a fact. (It can be verified by accessing Sprint Nextel Corporation's 10-K SEC filing). Virgin Mobile is
not an independent unit that operates with no oversight - it is subject to the directives of Sprint Nextel Corporation senior management.
So why would they care if you suck up the bandwidth? They don't have to pay to add new infrastructure.
Since Sprint Nextl owns 100% of Virgin Mobile USA, Inc., any problems, congestion, abuse, etc. caused by VM customers ultimately have to be addressed by Sprint Nextel. That could mean policy changes, enforcing some clause in the Terms and Conditions or spending $$$ on the network. VM's problems are Sprint Nextel's problems.
Under the old arrangement when VM USA was just an MVNO and
not 100% owned by Sprint Nextel, it's true that VM didn't have to make infrastructure investments, however, VM would have been paying to Sprint Nextel by the MB for your data usage, so VM would have had an incentive to drop the boom on you anyway. Sprint Nextel has 100% visibility of VM's customers and their network usage at the individually identifiable level. Being a VM customer won't "hide" you anymore.
Are there really any Virgin techs driving around in company vans working on cell towers? That's what I mean about who runs the infrastructure.
Since you asked... Sprint Nextel outsourced the installation and maintenance of its network to Ericsson, so the I/M of the physical layer is done by contractors (Ericsson employees). If that deal is structured like most, the Sprint employees who were doing the impacted functions were transferred in place over to Ericsson and are now doing the exact same work as before but are now Ericsson employees. (I have no insider knowledge about that particular deal, but that scenario is pretty typical.) I don't know what assets (such as vans), if any, were transferred to Ericsson. Because of liability issues with motor vehicles, the vans were probably transferred to/bought by Ericsson, otherwise Sprint Nextel could be sued by anyone who is hit by a Sprint owned van, even if it was driven by an Ericsson employee. Deals like this are complex and literally as thick as a phone book, so anything is possible.
All that stuff aside, if VM customer use of "unauthorized" tethering causes network problems, Sprint Nextel is going to know. Sprint Nextel would be very reluctant to spend money to fix a problem being caused by an "unauthorized" use that does not bring in any incremental revenue. The cheapest solution would be to identify individuals responsible and take punitive action. Punitive action could mean to specifically ban the practice and/or to disconnect accounts. If enough customers are doing it to justify the cost of creating a product ("Add tethering for an additional $10 per month!"), then they would probably do that. Corporate politics can get in the way, though, when executives say things like "If they have sophisticated needs like that (tethering), we need to ban the practice on VM, and transition those customers over to "traditional" post paid accounts on the Sprint brand. We'll offer them a free phone so they don't freak out as much. Blah, blah corporate speak, etc." I can only guess.
As others have said, use at your own risk. Tethering falls into a gray area of acceptable use as defined by the T&C's, so I just want us all to go into it understanding some facts and some possible consequences so that we can each make an informed decision.