[quote name='Danil ACE']I thought that the hddss.bin file was unique to each drive?[/QUOTE]
No, you only need the one that matches your drive size.
[quote name='RudyPants']And possibly get your 360 banned from Microsoft ... Sounds like an awful idea.[/QUOTE]
And no, you will not get your 360 banned. I have done this for two family members living in the same house with Gold LIVE accounts, and both of them play each other all the time without any problems.
For people who are lazy and don't have a drive at all, this deal is pretty good.
But, as larger capacity drives are supported in further 360 updates, a person with an "unofficial" HDD can change his out cheaper than someone without one.
Personally, if I owned a core model, then I would get the 20 GB version for $20 (or was it $30?) from MS. I would sell the 20 GB for whatever I could get and keep the casing for the 120 GB BEVS drive.