Interesting.  The source .wav was 44.1k;  I can confirm the .ogg output from a vanilla "eggenc source.wav" style command was indeed 11.025:

file brother-mouse_How-I-Got-Into-Linux.ogg
brother-mouse_How-I-Got-Into-Linux.ogg: Ogg data, Vorbis audio, stereo, 11025 Hz, ~44600 bps, created by: Xiph.Org libVorbis I

Looks like the default is to get aggressive with filesize based on aural content.  Maybe I'll pass flags to oggenc to force 22.05 or 44.1, or use mp3 in the future.  