Debian

In debian install-recommends defaults to "true", which means that you will get all sorts of unnecessary extra packages when installing software

Check the settins with apt-config dump

To circumvent this, put this in a file in /etc/apt/apt.conf.d/

APT::Install-Recommends "false";

Debian 6 & postgresql

In debian 6.0 psql is linked to the lesser developed libedit instead of libreadline, see this.

It can be bypassed by launching psql like this: LD_PRELOAD=/lib/libreadline.so.6 psql