The documentation could apply to older versions still or just be outdated.
The latest documentation for Maverick is in a new font and theme and not
everything is updated to this yet. You will still find occasional references
to versions that are no longer supported and to Synaptic and as of 10.10
Synaptic is no longer included with Ubuntu. Things in Ubuntu are moving very
quickly and documentation cannot keep up, but it shouldn't really because
there are so many versions of Ubuntu still in use, so no documentation can
be wholly current. The Ubuntu Partner programme is fairly recent. Before
that time there was no way to get proprietary software and Ubuntu did urge
people to go outside the repositories as necessary. If this was still the
case, there would be no need to include Skype in the partner repositories as
it would be a redundancy. I could be wrong on this, but it seems to be part
of a trend and may include paid programmes in the future. I'm sticky my neck
out on this one. :)

Personally I have nothing against installing from outside the repositories,
but it should only be done when necessary and by people who know what they
are doing. To blindly follow instructions that you do not understand is
counter productive in the long run. If you advise someone to download and
install a DEB and they do not understand the process then they will wonder
why they can't update it or why they might have a future dependency error.
The Partner programme uses Ubuntu's repositories and therefore it keeps
things uniform. You should get updates at the very least. This is progress
and people should be encouraged to use the most progressive approach as a
first course, IMO, as it reflects the future of the operating system.

The latest thinking in Ubuntu is to move toward everything being available
from Software Centre and being newbie friendly. I still use Synaptic and
don't like the Software Centre because I like to check on the dependencies
and origin, etc. Like many users, I don't like dumbing things down, but
Canonical is on its own course to supplant Mac OS and like it or not that is
the future for Ubuntu. They want to be inclusive and that means more
proprietary software. Also you will have noticed that as of 10.10 it allows
the user to install proprietary drivers and codecs just by checking a box at
installation. This may seem like their answer to Mint which was eroding
their user base, but it is more likely that Ubuntu has moved away from their
tradition fence sitting stance in the hope of being inclusive. I hate that
word, but it seems to be where they hare headed. They want to appeal to the
most users. Look for some of the default settings of Ubuntu to change in
11.04, Natty Narwhal. Many will be things to improve security and
convenience to the user.

I do not use Ubuntu because I do not like GNOME and will not have Mono on my
computer. Ubuntu 11.04 has increased Mono by having Banshee as its default
music player. One more reason for me to not use it and stick with Kubuntu
where sanity reigns. I do follow Ubuntu closely though and am as interested
as anyone on where Shuttleworth and company is leading. Although I do not
like some things, I at least appreciate someone showing some leadership and
setting a different course.

People are welcome to follow any advice they want and even destabilise their
systems. It is their freedom of choice. You just won't find me advising them
to do it. Of course, that does not apply to me, because I seldom follow my
own advice and am often in trouble as a consequence. But by now I have
broken my system as many ways as possible and can get out of almost any jam.
So take it for what it is worth. But, I bet most people did not even know
that Skype was in the repositories if they only ticked a box in their
sources. That is why I advised it in the first place. I also think that we
can avoid future problems by encouraging users to follow standard practice
whenever they can and only step out of line when necessary and in this case
it is no longer necessary.