Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
In the past we could divide Linux distributions in two main categories, the livecds and the installable ones, nowadays we have a third category, the D.T.C.R.F.C. or 'Distributions That Can Run From Cds'.
The main characteristic of the livecds is the possibility to run your system without install it. In fact, all DTCRFCs are able to run without previous installation and it confuses users around the world, even the most experienced. For those I would like to input the second main characteristic of the livecds: the power of costumization.
The livecds not only must run from any external devices, but also have to let the user rebuild them without lose precious time, need useless efforts or start bark at the moon, and the DTCRFCs do not provide the second characteristic because they are installable system built to act like a livecd.
The DTCRFCs I tested run incredible slowly, spend almost five minutes to boot, do not have a single application to rebuild the ISO on the fly, start useless services and love when we install them to the harddisk. They do not share the spirit of the livecd family members.
There are some livecds, important ones, without the power of costumization necessary to become user friendly, but at least they are livecds, they are distant cousins of the really good livecds, allthough some of them are becoming DTCRFCs.
In my personal opinion a livecd most provide a Modular System. Slax and Morphix provide different flavors of modular system that can be used to build a livecd. A single file with more than 650 MB including everything of the livecd does not help anyone. A livecd ISO must be easily edited.
If you intend to test and install a distribution, you can use DTCRFCs, if you intend to have a livecd, do not download some of these famous DTCRFCs around the world, get a REAL livecd, run it, rebuild it, remove and add modules, save settings, play around, make your own personal livecd, own modules and study the power of costumization.