Comment 3 for bug 63116

Use Case

If a directory had files foo1, foo3 fooN+1 but no foo2, foo4 foo5.
(Just to make the example work better, assume all files are big enough to call for 20 seconds copying time, and it will cost you several minutes to restore them all.
Jane happens to know all the files she wants are on filesystem /bar, knows that some files are missing but not which actual files.
So Jane can "cp /bar/* .", this is far from optimal, as this will this will overwrite all files in the location where the missing foo lives.
So Jane has the setting in .bashrc, "set -o noclobber".
noclobber will prevent any overwriting of files that actually exist on the system.

Only howto I can find that makes it easy to read:
http://www.linux.com/guides/abs-guide/options.shtml