I am thinking of buying a couple PS3 PSN games from the US PSN with a US PSN account since they're having a sale.
I download the games, and then switch accounts to my main (Australian) account, would I still be able to play them and earn trophies etc?
Best Answer
Yes. As long as you've "activated" your console with the secondary account, you may use the games and DLC bought in it by different users on the same console.
There may be some exceptions to this (I know of a single game and a couple of DLC), but to be on the safe side, on the store's product page, look for the disclaimer
For comparison, here's what the disclaimer on a "single user" game looks like:
(Emphasis mine)