As I have mentioned earlier T-Mobile's fair usage policy barely exists. You could easily do 2GB a month for your whole contract without them caring. I used to break the limit constantly with my G1. I tethered 3 computers via wifi for a few weekends at a friends (no landline.) A few played WoW whilst I played Trackmania, all through my G1. I even downloaded the beta of Windows 7 (4 GB) through my MSDN account. Whilst pure data sims don't have terms & conditions regarding Skype & Tethering, they are expensive (£15 for 3-5GB.)