But these movies made for your computer are going to look rather crap on a 50" Plasma. Having it 50" diagonally would only accentuate it's crapness.
I can see streaming videos being OK for standard definition TV though. Most people still have these types of TVs, so the images will still look OK and/or not too small.
This would normally be true, but I have every one of my 300 DVDs ripped to a full resolution Quicktime H264 file and stored in my iTunes library, something I believe iTV would see rather nicely and stream over 802.11n. I have it streaming into a Mac Mini running front row into my TV now via gigabit ethernet from my Power Mac MDD. Not to mention video podcasts and TV shows are in 640x480, a resolution I normally see on my HDTV without any problems.