I have a question about that. It is required to link your PSN account to your SE account. However, you can play games with several PSN accounts on the same PS3 as long as it was purchased and installed with one of them, correct? Or Doesn't that mean I could link, say, my GF's PSN account to her SE account using the game that I purchased with my PSN account (and linked to my SE account)?

I haven't tested this in release, but in Beta I had to download the client using a throwaway US PSN code because my canadian PSN account didn't work for it. But I played the game, and linked my SE account using my main, Canadian PSN account which was not used to make the "purchase".