I found a discussion thread:
which talk about the iTunes bug when calculate the free space of iphone.
I think the problem I meet should be from the same root cause.
My iPhone is almost full, (with about 4G of free space). And I have lots of photo to sync.
When it try to sync, (I guess) iTune will think the free space is not enough, so it just drop some photo.
And this makes some of my photo lost randomly.
The bug exist for about one year from iTunes version 10. (I can't believe it .....)
I just hope (and pray ?) Apple will fix it soon.
Right now my temporary solution is sync the photo in several times. This controls the mis-calcuated space
to be within my free space. This temporary looks work. (but stupid of course).
I also delete some of "big game" which make me have more space. Theoretically this should also help....
I have another trick to avoid such problem, maybe you can try it temporary.
You can try remove the failed album => sync => add the album back => sync.
I also meet similar problem on my iPad ( photo lost), but not as serious as iPhone.
I use the flow and solve the problem temporary. Maybe you can try it ~