I only have 3 games, lol. so I don't need the covers update, and I may have port 11222 for dean's gui server open, and 21 for blackbox, but I like to keep all my ps3's on the home network sharing things with my windows computers, and other things. I put a sniffer between my Modem and Router, with a good firewall so I could stop traffic if needed, and that seems to work well holding the PS3 back.
I read a post once and as silly as it sounds, the PS3 will find a way though your network regardless. I thought it was funny as well, until I read up on what the Jap's have been doing over the last 10 years with their software and hardware spying on their customers.
Sorry a bit of topic..