Yeah, I've noticed that too. By the way, I didn't install the vending.apk, or whatever the name of the apk file for the Android market is, manually. Mine was pushed to my phone. I just noticed it when I rebooted my phone and checked the market the other day.
Yeah what happened to me was i was updating apps then market crashed i opened it back up and it had updated itself without even telling me there must be something hidden in android that tells market to auto update
I guess so. Anyway, it's not really a big problem for me as long as my apps get updated when they need to be. It's more of an annoyance when it crashes and you have to re-download and install the apps manually.