Why 2012? The satellite that LiveTV will use hasn't been launched yet. From previous experience with the long delays in Inmarsat's 4G BGAN satellite launches, betting on having a bird in orbit is fraught with difficulties.
This all seems a bit odd. Next year is a long way off when competitors like Delta have Wi-Fi today. Relying on an unlaunched satellite is tricky, coupled with a firm that doesn't yet provide Internet service, and with the "over 200" and "starting in 2012" qualifiers. United won't have substantial Internet service on its planes until 2013 or 2014 based on all these factors.
It's a way to issue a press release like something is happening.
The letter of intent part is interesting, too. Alaska had a letter of intent with Row 44, but ultimately opted for Aircell instead. Connexion by Boeing had many letters of intent; few were executed.
JetBlue Sets Mid-2012 for In-Flight Internet