AT&T to credit $100 on each Nexus 7 with data plan till Valentine's Day, 'cause it loves you
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Essentially you end up with a 32 GB Nexus 7 for two Benjamins instead of three, but have to either add the tablet to an existing Mobile Share plan, or signup for a new postpaid data subscription.
Not that cheap in the end, as you'll be shackled for two years, but if you were going to do it anyway, this is a good deal, and will run through February 14, that's how much AT&T loves you.
source: GooglePlay
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