I think I figured it out (I hope I don't sound TOO naive to those who live on the Usenet). Supposedly, each Usenet news server has a newsgroup subscription list. Worldwide, there are literally thousands of them. When a person posts a message, it gets sent to their ISP's news server, then later sent out to others across the Internet. Eventually, all servers that subscribe to the same newsgroups get each other's messages, perhaps taking several days to complete the circuit. Also, some servers have longer message life cycles (the time it takes for a message to expire and get scrolled off the list). With all of this in mind (in addition to different time zones), it would explain why some people respond to a message nearly a week after it had been posted, while others respond the very next day.
What do you think?
-Gary K.