Well, it's right that blaster or any other worm
could expose your system, but this worm attacks
indiscriminately so there are tons of infected
computers and a hacker would never try to collect
info for everybody. A virus that wanted to do this
would have it's own entry system instead of having
to relay on an entry point created by other virus.
A different thing is if the attacking program is
specifically targeting you, in this case it means
that someone "not ramdom" is trying to hack you
(that's what happened to your daughter's website)
and everybody is exposed to this kind of attack.

Even with the badtrans virus it was demostrated
that the virus was prepared to steal info from
specific places, so it was not "that random" even
it's true that everybody had the risk to had their
info stolen.

What i mean is that blaster didn't steal any info
and even leaving an open door on your system it's
just one more of the ones that you already have.
If you ask why blaster leaves that open door,
then, the most probably reason is that the person
who created it wanted some specific places to be
infected and this way become vulnerable with an
opened door that he/she knows how to use and this
way enter the system.

Of course, this doesn't mean that your sysop
doesn't have to be worried about the situation, an
infected system is a risk for the network and has
to take measures.... what they told you is just an
excuse. You see, the definition of worm in the
virus context is basically just a program that
wants to infiltrate and propagate to other places
consuming the host resources in the process, what
can be annoing sometimes. Of course there are
exceptions but most of this worms don't damage
your computer (even they can be annoying). For
example, blaster just uses your computer to launch
DoS attacks to windowsupdate (of course there was
a bad side effect of the computer reseting because
of the vulnerability used to enter the machine but
that wasn't the pourpouse of blaster, just a side
effect), then sobig just uses your computer to
transform your PC in an spam generator without you
knowing about it.... 

heh, I even know of people that if told them that
blaster just makes attacks to microsoft sites they
would say "So where can i find more of those
programs?", so a reason more than enough for
sysops to not tell the entire truth, i mean, worms
are basically (always with exceptions of course) a
threat to the whole internet as a comunity, not to
the specific infected computers.

oh well, i prefer to stop talking about this
off-topic thing here.... Well, just say, even all
what i said before is true that doesn't mean we
take worms lightly, they are bad things and should
be treated as they deserve.