http://arstechnica.com/apple/news/2010/04/ipad-3g-wifi-day-is-today-heres-our-data-plan-primer.ars
Activity Average Data How much does 250MB get me?
IRC 0.14MB/hour 1800 hours (or 75 days)
E-mail 0.02MB/e-mail 17,000 sent or received
E-mail a photo 0.39MB/photo 640 photos
Web Browsing 0.54MB/page 460 webpages
Lookup Map 0.20MB/map 1280 map searches
Check Twitter 0.06MB/check 4,100 Twitter checks
Words with Friends 0.10MB/round 2,300 rounds
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