Well, if you guys read the whole story.
What happened was during the FIA Stewards Investigation they asked the team if they told lewis to let Trulli through, they said they didn't. They then asked Lewis and he also said no such communication had been made.
Shortly before going to the stewards Lewis told the press that the team told him to let Trulli past.
The Stewards re-opened the case and checked the team radio transmissions and they felt that Lewis and Mclaren had misled them during the first investigation.
Trulli however said what happened how it was, lewis slowed down off the racing line so he passed him, on the next strait he pulled over and slowed down to let lewis passed just incase his intentions of slowing down off line where not to let him passed.
Lewis told the stewards he had not intently let Trulli passed and that the team didn't tell him to let him passed either. This was not true and lying or misleading FIA stewards should lead to a heavy punishment, if you ask me just a DSQ is light!
http://news.bbc.co.uk/sport1/hi/motorsport/formula_one/7979304.stmVideo evidence of the situation.
http://dl.groovygecko.net/anon.groovy/clients/igentics/australia09/2009_Australia_Hamilton_driveraudio_final.mp3Hamilton's team radio over that period.
http://forum.planet-f1.com/index.php?t=msg&th=74407&start=0&FIA notes and transcripts.
Looks like he was in the wrong to get 3rd place.