I don't know where else to post this so here was my problem on Fedora 17:
I changes my fonts to Droid Sans with the Gnome Tweak tool (installed from Live CD btw) and everything was great until I installed VLC Media player (and other software like Skype).
The menu fonts in VLC were horrible... way too big. They were at least 2pts bigger than they were supposed to be (ok, maybe not 2pts but close). I tried using the accesability menu option to adjust the fonts to no avail.
Then I found:
And discovered that the DPI was 72 while Gnome 3 was 96. Derp!
I changed it to:
<edit name="dpi" mode="assign">
And everything is fixed.
Not sure if this issue came about due to my font fiddling or if it was there from the beginning.. but wanted to post about the issue quick so others could find it without searching high and low on the interwebs.
At any rate .. First I've tried Fedora for a VERY long time. I'm glad I did =0)