My TiVo, along with the rest of my home LAN, sets behind a firewall appliance and I'm quite cautious about allowing unknown connections.
After the Yahoo! and other apps were activated, I had to analyze my firewall logs and write rules to allow the TiVo to establish contact with the various servers for Yahoo!, Fandango, Live365, etc. I'm not sure I got them all as I haven't really had much of a chance to play around with the new apps and this trial-and-error approach is an annoyance.
I'd really appreciate an on-line list of ports and IP addresses which my TiVo will be connecting to plus any inbound ports and IP addresses which may want to connect to it. This information will allow anyone behind a firewall to provide required access while still maintaining security.
If/when new apps are added, the list should be updated accordingly.