What? I suppose if you always want to name your latest class foobar, then yes, but then you have other problems... If you properly pick a classname you almost never need to rename it let alone the methods contained with the class. Plus namespaces are going to introduce their own sets of problems where extension X adds namespace X, which some lib already decided to use and we are back to where we are at today.
import('org.phpdb.propel.runtime'); or whatever. How could that possibly collide. Come on, "people might use namespaces in a wrong way" really is not an argument against them.
David