I'm trading a friend's ETrade account the past week or so. Not sure why this is happening, but I've been high bid all alone on a few things and sell orders are being filled elsewhere at my price -- it seems to be happening much more frequently than when I bid through NITE or AUTO with my other accounts.
I seem to remember Lance or someone saying a year or two ago that ETMM was always the last bid or offer left, like other MMs preferred not to deal with them until there was no other choice.