For the Photosynth team, just to reword what Joscelin is reporting here, the issue is that the specific phrasing of "Show on current frame only" is potentially confusing for users.
Here's an example scenario.
1) User creates synth with 30 photos in it
2) User places a highlight on photo 15 with visibility automatically set
3) Later, during synth playback, the synth author pauses the synth on photo 10 where the highlight attached to photo 15 is still displayed
4) Synth author enters the highlight editor from image 10
5) In the highlight's visibility options, the phrase "Show on current frame only" is given as an option, however if selected, this will limit the highlight to only being shown on photo 15, rather than photo 10 (where the author is currently navigated to).