From Major Nelson’s Twitter (via team-xecuter.com):
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Be careful folks! RT @Stepto Hrm. I spy with my little eye some *illegitimate* ODST players. No early play for you. Commencing permabans.
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*Update* Seems like Microsoft claims they can detect illegitimate copies. Xbox Live Chief of Police Stephen Toulouse told kotaku.com:
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I can be clear however that this applies to illegitimate copies only, the ban covers the Xbox LIVE account and could possibly include their console depending on the results of our investigations (which are ongoing). We do this from time to time with titles to combat piracy.
If a user happens to purchase a legit copy of Halo 3: ODST early, then our problem is not with the user but the retailer who broke the street date. Those individuals will not be punished.
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From joystiq.com:
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In a column published today on Develop, Black Rock Studio (Pure, Split/Second) technical director David Jeffrries revealed that Microsoft has removed an item from its TCRs (Technical Certification Requirements) that stated all Xbox 360 games must run at a minimum of 1280×720 (720p) resolution if the system is in HD mode. According to Jeffries, this was done earlier this year so that developers could be “free to make the trade-off between resolution and image quality as we see fit.”

Joystiq has confirmed with a trusted source familiar with Microsoft’s TCRs that Jeffries’ claim is legit. Not only that, but, as of March 2009, Xbox 360 developers are no longer required to utilize full-screen anti-aliasing in their games. The elimination of both requirements is especially noteworthy since the console maker had touted that all 360 games would run at a minimum of 720p with at least 2x FSAA since before the hardware launched.
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Full Story: joystiq.com