Wikipedia (obviously the last word on any subject) says about beer tannins that they are acceptable in some styles (they mention Flanders red, nice touch) but not in lagers. They also say that tannins and combine with proteisn to form chill haze.
My thought is that the scum is definitely not all tannin, but may contain some complexed with denatured protein. Whether it contains more tannin than the non-scum coagulate I can't say, obviously there is some small difference in the materials since you don't continue to get scum forming if you skim it initially. Now how much tannin is in your beer in the first place, is something we have some control over through our crush, attention to pH and sparge methods. So if theres little tannin to begin with, then it would seem a moot issue as to whether the scum (or braun hefe for that matter) might need to be removed to avoid an off flavor. We know that some people put the breaks in their beer to no ill effect, including chill haze. Even if you have haze, you can remove it by fining and thereby remove the tannin component.
I'd think a little tannin might complement more beers than it fouls. Its certainly a major component of wine, and one that important to the flavor and mouthfeel.