Enough with the dynamite analogy: I never suggested that people should be able to "blow up" their systems with full root access. Indeed, it's precisely this attitude - that wanting to do only a little more than currently possible is somehow the same as "wanting it all" - that undermines any discussion on such matters and drives people towards exactly the social and institutional workarounds I already described.
It's interesting to hear the claim that most systems - presumably Unix-related ones - are now single-user systems. Even if that is the case, giving people the ability to customise that environment without having to nag the administrative staff all the time is surely beneficial. Indeed, what has often happened is that people on those traditionally single-user Windows systems have been able to more or less install what they want, with all the accompanying consequences, whereas everyone else has had to make do with what they're given.
If people could just apt-get a package and have it installed in their home directory, it wouldn't necessarily affect the other users at all. Of course they could fill up the disk with a complete installation of GNOME or whatever, but that's what quotas are for. (Although I now expect to be told that quotas are archaic and people virtualise entire systems to get the same effect for this as well. If so, Linus Torvalds and the GNU project maintainers should consider slashing away at the realms of apparently dead code that no-one seriously uses any more.)