My server gets 20,000 people updating their spybot per hour... There are currently 22 mirrors, and most of them probably have a similar ratio.
Unless you are talking a mass cluster, it wouldn't be very logical to have one server do updates. Additionally, the servers are all over the world. The US or Europe are not the only ones having spyware issues. A server closer to you will give you a better download rate, at the ratios above, a unmetered gig ethernet connection would be required... that would be some serious hardware to handle that.
I donate my resources, 40 MBPS on a high quality, power backed up server, would cost several hundred dollars a month. The only thing I get in return, is knowing that I am supporting the best anti spyware program out there, that is given out free for private use.
Every time the mother in law calls, or the brother that knows too little about computers calls, I put spybot on, immunize, and run a scan, and problems get fixed.
Thanks spybot. I'll set an HTB TC script to boost bandwidth on wednesday mornings as not to bother people from having to download an update twice.