The real issue is there is actually NO standard for rms levels for finished masters.  The good thing about the movie sound world is there is and it is -20 dB rms. But as far as CD's goes it is anyone's guess.
 
We are trying to educcate clients and hopefully things will move to a more reasonable standard level but konradh is very correct.  I do a lot of mastering myself and if I created K-14 masters most of my clients would not be very happy at all.
 
-16 seems to be a level that iTunes will work nicely at (as long as 'Sound Check' is switched on though)
I have mastered up as high as -8 to -6 dB rms for the Hip Hop guys around here and they are happy.  But it takes a serious limiter to do it though. (like PSP Xenon but at a price!)
 
I really like going for -10 dB rms though.  It seems to combine loudness with punch and transients if done well. Depends on the music too.

This article in Sound on Sound is really helpful in explaining the new loudness standards that broadcasters will be using. 
 
This is an earlier article that explains dynamic range and the "loudness wars."