Comment...You do have to switch your LAN to the same encryption if you are using the PS3's wifi to get online. Even though the PS3 and PSP are peer to peer, once you add the encryption, it will no longer get on your "open" home LAN. And how do I know? Because I had to change all of my home LAN just to connect the PSP to the PS3. What a pain. 64 number encryption is a lot of button pushing using the PS3 controller and the PSP. And I have two laptops and two wifi desktops that I had to do this with as well to get everything on the same page. That was a long night. And the next day, I changed it all back. It seemed to make my computers a little slower when on the internet. Some delays and what not.
I don't plan on purchasing any of the online psx games, so for now I'm not worried about the PSP hooking up with the PS3.