2) User clicks download link, drags to any directory they want.
Trying to build packages that continue to work across releases and as libraries get updated and packages change -- and operate in a compatible manner with the built-in packages -- is surprisingly difficult.
Why don't more people do it? The only 3rd-party packages I come across are RedHat RPMs, and half the time, they're broken. I almost never come across 3rd party apt/yum repositories run by corporations, and the few times I have, they've been very broken (remember Ximian? http://en.wikipedia.org/wiki/Ximian)
