From my tests, followSymLinks that is used to delete the content of symlink when it is set to true, is not taken in account.
It should be a regression caused by http://jira.codehaus.org/browse/MCLEAN-28
This is a blocker bug, since it could delete all the filesystem easily, and there is no workaround. Even when I set followSymLinks explicitley to false, Maven clean 2.3 follow symlinks and delete its contents.
To reproduce :
Declare 2.3 clean plugin in your pom
mkdir /tmp/test
touch /tmp/test/foo
symlink -s /tmp/test /myproject/target/test
cd /myproject
mvn clean
After runnig that, /tmp/test is empty !
If it is confirmed, I would recommand to release quickly a 2.4 version with a fix, since in is REALLY dansgerous.
The only workaround I have found is to use 2.1.1 release.