Install as little as possible
Currently, debootstrap installs the at-Daemon. Because of this, it has to install mailx. This in turn needs an smtp mailer, which is by default exim4. And this one needs lots of libraries for gnutls etc.
Later on, in tasksel, "Mail Server" is then already selected, despite the fact that the machine probably isn't meant to be a mail server.
None of this is true in Etch, AFAIK -- JoeyHess
by not installing at in the first place (only a few need it anyway) we can get rid of a bunch of packages.
also, people would be able to install the mailer they want manually, e.g. postfix or esmtp
this error happens also with the new cdebootstrap.
Workaround
When you use the CD method of the new debian-installer, you can create a file .disk/base_exclude with this contents:
at exim4 exim4-base exim4-config exim4-daemon-light mailx pcmcia-cs setserial info libident libgnutls7 libgcrypt1 liblzo1 libopencdk8 libtasn1-0 liblockfile1 libpcre3 libpcap0.7 tasksel telnet libtextwrap1 ipchains ppp pppoe pppoeconf pppconfig
to make the installation lean.
Unfortunately, this doesn't work with the ?DebianInstallerNetbootPXE method. You'd have to change the debootstrap udeb to achive a similar result.
Alternatively, you can use a udeb (i.e. bootstrapwrap.udeb) that provides the same feature by including a wrapper for debootstrap. This can be downloaded in the early_command (see the middle of this early_script for an example), along with the base_exclude file. More information about how this is used can be gleaned from reading the READMEs & HOWTOs: http://hands.com/d-i/