Would it be safe using debian to do run a weekly cron job to "apt-get update" and "apt-get upgrade" on a server? I don't know if there are problems I could run into doing this.

Although I don't think it would be 'unsafe' so to speak, I wouldn't really have thought that would be advisable... If it aint't broke don't fix it... I think you would be better to do upgrades manually and only for those apps that you know have a bug/security flaw or you need any new functionality.

It should be noted that I don't have any servers to look after so I could be wrong, what do others think?

I'd rather be able to see what updates were going to be applied, and pin those packages I want to keep 'just in case'. Setting it to automatically update on a server bright bring down some network functions. Although there shouldn't be anything major changing if you're running Debian stable other than security fixes (since new releases won't get added to stable), I'd rather be able to see what's happening. If you're running a server out of testing then you're much more likely to encounter problems.

If you're managing servers, it's adviseable to take time out each week to check over your log files, make sure there's no obvious problems, run your updates, etc. It shouldn't take too long - it's probably a 15-20 minute job on each of our Linux boxes, but we then have peace of mind everything's working, and can plan any maintenance that needs carrying out if we spot hand drives filling up or signs of drives / memory failing, etc.

If the server is running stable you would only be getting security updates when it is updated so you should be safe. Instead of re-inventing the wheel you may want to install the cron-apt package.

After seeing what apt-listbugs identifies in the Sarge updates as being grave/serious problems, I would be very reluctant to do auto updates, even with stable.

With Etch/testing, auto updates are really out of the question these days, given that apt-listbugs tends to identify a lot of updates with very serious problems. An awful lot of kde setups have been compromised by bugs in the updates during the last month or so.

When I look through the bug lists, I have to wonder whether this is going on in FC4 and we don’t know about it.

Didn't know about cron-apt. I'll look into that.

Well after reading cron-apt install pages, it doesn't recommend doing an automatic install of all packages using that so I guess maybe that is some proof not to. :P