> Besides, snapshots often contain uncommitted tweaks, so a cvs tag > would not even do the job for you.
About once a month there is a day where snapshots are a completely unmodified source tree. The other 29 or 30 days of the month, there are small "needs to be tested by volunteers" diffs put into the tree. This also serves to ensure that none of the architectures get busted, because those snapshots are also then rebooted on the build machines, and thus tested. With about half a million dollars of extra money I am sure that I could change this process and make it more suitable to the whiners.
