HDTVs that claim to be 720p are usually 768p.
At least you get a little more rather than a little less, not that it helps much when you want the pixels to be exact. Never bothered me though, usually when it's that close it's only vaguely fuzzy at worst to my eyes.
The Xbox suggestion shows why (as I recall) this happens actually: I BELIEVE it was done to comply with XGA standards
, though I see 1280x720 there so it's somewhat baffling.