Grey out scrollbar button when border reached?

Hi!

I remember someone claiming on a kde-ml about no visual feedback whether
in huge lists one already scrolled at the end or just misses one,two
lines (searched for a reference, but failed). I then already agreed with
him nodding my head, but being made sensible about this I since then
over and over again have met this problem.

Today it just struck me: Why is the corresponding scroll bar button not
simply greyed out when the view has reached the corresponding end? 

Would be consistent with the rest of the user interface, and signal
whether you are or are not at the end of the view. I still have trouble
whether this would be acceptable from an aesthetic(word surely
mispelled, where is my dictionary) POV. But might be a question of
usage...

What do you think?

Friedrich