I ask because I have traditionally used TeTeX, which is perpetually included with Slackware Linux. However, I downloaded the source code for TeTeX, and it appears to be a bit tricky to build on Mac OS X, which I now use 99% of the time. As a rule, for security reasons I don't download prebuilt binaries from just anybody—I need to build it from sources myself.
Building an entire TeX distribution from source is a somewhat daunting task, but since TeX is open source, it is possible to do it. The place to start is:
However, open source software is also built on trust. If the binaries come from trusted sources there isn't really much sense in not using them. The MacTeX builds are created by Dick Koch at the University of Oregon. You will save yourself a lot of trouble by putting your trust in his (and all the other TeXLive developers') skills.
I will risk here to alienate many TeXLive contributors and users (one being myself) and mention a new minimal, ultra portable distribution of TeX and friends for Plan9 and Unix operating system. It is called KerTeX and should be trivial to compile on Darwin/OS X. I would also imagine that somebody had a working port (BSDs users know what I am talking about) of TeXLive for OS X if not in official MAC ports tree.
My suggestion would be to go a slightly different way -- I use Macports (http://macports.org) and that has a really large selection of open source packages available for download and install. It keeps track of the dependencies and if they're not present will download and fetch them for you.
For me, getting the full texlive install in Macports was just issuing the command
sudo port install texlive +full +doc
and then letting it chug its way through to completion.