Ubuntu 8.04, The Hardy Heron, continued
Counter-intuitively, these good intentions pave a Yellow Brick Road to a tyranny of petty autocrats, from System Administrators, Wheel wizards, sysops and uncertified power users, down the ladder to mere peons like secretaries, CEO's and college presidents — Hell, in other words, if you have ever dealt with a rogue employee with access to systems you yourself do not understand.
Macintosh OS X — a species of OpenBSD Unix, after all! — solved this irritant once and for all, by stuffing the entire list of "needed to run" components into a folder which the OS recognizes as a single, opaque application bundle that can be fired up by ANY user, "qualified" or not.
It's the difference between object oriented (Macintosh, modern, sane, good) and static global (Linux, archaic, crazy, bad).
This is even worse when two programs you might like to run under Ubuntu rely on library elements that were written years apart. Thus, program A needs (say) Python 2.4, while program B requires Python 2.5. You'd think A could use the later version of Python, but no, it can't. So now, your global /usr files are bloated with multiple versions of the same libraries, and Heaven help you if old and new versions happen to contain similar files with different dependencies! Pause. Consider.
Package managers are supposed to help with this, but they're a kludge, a stopgap automation which only works by implied consent to "best" practices under a chaotic regime.
This is why Linux sysops tear their hair, and why casual users are at the mercy of the vagaries of history. Until Ubuntu wises up and implements something similar to the Macintosh application bundle, running Ubuntu is like running with the cave bears — a thing no modern man or woman should be forced to do without grenades.