I often create 2d histograms with log x or y axis.
The hist2d function uses the pcolorfast method which can not handle log xy axes.

The following code explains this issue:

from pylab import *
axis = logspace(-1,0, 10)
hist2d(rand(100), rand(100), bins=(axis,axis)) #this still looks as it is supposed to look
xscale('log') #this scales only the ticks, but not the histogram

This could be fixed by using pcolormesh instead of pcolorfast in axis.py.
If there is no specific reason for using pcolorfast instead of pcolormesh I would propose to change this.

I'd be happy to create a fork and submit a pull request (it's only one line ...).

Thanks!