To all you PSN players, the Trophy update has been released today, but sadly Criterion were not able to implement them retroactively.
This is what Criterion Games said on their website today:
"Burnout Paradise saves are locked to your profile. We had hoped to use this to retroactively award trophies, but we discovered during testing that this is not possible. You will therefore require a fresh game-save to receive trophies in Burnout Paradise. If you're familiar with PS3 trophies already, you'll recognise that this works in the same way as all other games that have added trophy support post-release."