Some major Linux distros use Python for maintaining their packages. Red Hat (and its downstream distros) which use the yum tool uses Python 2.4. I tried to install Python 2.6 in CentOS 5.4 without success. The tool rejected to install Python other than 2.4 using that tool out of fear that it will interfere with the tool.
I just found another catch, when you are trying to install Python 2.6 in Ubuntu (I was using Karmic Koala, 9.10), such as:
$ sudo apt-get remove python2.6
It will display the components that are about to be removed.
Kids, don't try this at home!
It will remove your whole desktop related application! Java, Gnome, apt tools. You practically will be left with command line Linux, and without the apt tools.
Uninstalling Python 2.6 from Ubuntu seems to be an act of shooting own's foot!
Lucky I tried on not-so-important experimental Ubuntu installation on my laptop.