couple of things... most have been mentioned, but anywayzz..
I've only encountered this 3 times in my life, the most recent occurrence was 2 weeks ago..
I was asked to take my shoes off at my mates new appartment, so i did as that was the norm there apparently,
so i moped around on the carpet and kitchen lino, my feet freezin while they all had nice snug slippers.. Didn't feel overly happy about it all to be fair.
If and when I go there again, i know now to bring slippers with me.. funny thing is, they have organised a bangin techno party for NYE, so If this goes down with people pissed and pillin, then the shoes issue will be the least of their worries. Actually, it would be rather funny to see a bangin techno slippers n socks party

I was in France about 4 years ago and they had a tradition of doing the same thing, but in the doorway there were about 10 pairs of slippers.
So everyone got a pair of slippers to wear, no complaints, everyone happy..
Thing is though, the germ thing is totally stupid, as has been said in here Kids and adults need germs to build up the immune system, if we all live in protective little havens we would all be sick much more often. The argument that wearing socks instead os shoes would carry less germs around is a little, emmm, how do you say it best... misinformed.. silly... insane?
I know a few lads that I would pay my weeks wages to so that they keep their bloody shoes on, fear of stinkin the place out gotta be on your mind from time to time surely.. Not everyone has odourless feet, and not every girl likes their feet, i often hear its the part of their body they hate the look of. So i can understand that girl not wanting to take them off... but ofcourse, she should have said it nicely, rather than abruptly. But again, this depends on the culture too.. I know over here we apologise if someone walks into us, never mind the other way around, i guess we are overly courteous and so forth, but i dont have a clue of how people behave in Sweden.