Open Source is a viable alternative to commercial closed-source software, and both can be used for the purpose of setting up a web site. Although various software packages have different qualities, Open Source has both the advantage and drawback of putting the user in charge. This means more responsibility.  By accepting less responsibility, however, you're at the mercy of manufacturers when things you install don't work, when you discover a bug, when you find out that software won't do what you want it to do, when you discover that the nicely printed manual describes only the pulldown menus , and/or when you can't locate information on how to setup an important option. You may even find that the manufacturer has changed the licensing policy and from now on you have to pay a yearly fee to keep using the software, or that the manufacturer has altered all your web pages to make links to its own (see www.slashdot.org/article.pl?sid=01/06/07/1252227, which describes the Microsoft "smart tags"). Heck, with Linux, you can keep Windows or Mac on your system and run it in a window in the background with a low priority. The best of both worlds !
So, believing in controlling our own destinies, and that the Open Source solution is superior for some applications and at least equivalent for many others, we've chosen to spend our time with LAMP. Even Apple has seen some light at the end of the tunnel and released a new operating system based on BSD; the underpinnings of the system, Darwin, are Open Source, and Open Source programs can be ported to it.