itTV won't show video because ITTF doesn't have the rights for the Olympics. They will provide results, live scoring, stories etc., but no video.
NBColympics.com will stream up to 4 matches simultaneously. However, access requires verification through a US cable provider - a user needs to be a subscriber of a cable package that includes MSNBC, CNBC etc. This is different from 2008 and will most likely present an additional obstacle for international users. It is not just a geographical restriction as in 2008.
CCTV 5 will probably be much easier to access (via TVU etc.), but I doubt they'll show any TT until the final rounds.