There is nothing dangerous about apt-get clean. It _ONLY_ cleans out just-downloaded packages. Any operation by the application manager or apt-get that needs any package(s) removed by apt-get clean will automatically re-download the package. apt-get clean simply flushes a local cache. It's utterly safe, unless you intend to never again connect to the network.

Of course, 'sudo gainroot' implies some danger, if you execute something different than 'apt-get clean'.

What _is_ dangerous is that 'rm -rf' command originally suggested. Now that one is one to avoid at all costs. One typo and your system is viped out.