Ownership of address space (posted 2002-06-30)
In the first week of May, a message was posted on the NANOG list by someone who had a dispute with one of his ISPs. When it became obvious this dispute wasn't going to be resolved, the ISP wasn't content with no longer providing any service, but they also contacted the other ISP this network connected to, and asked them to stop routing the /22 out of their range the (ex-)customer was using. The second ISP complied and the customer network was cut off from the internet. (This all happened on a sunday afternoon, so it is likely there is more to the story than what was posted on the NANOG list.)
The surprising thing was that many people on the list didn't think this was a very unreasonable thing to do. It is generally accepted that a network using an ISP's address space should stop using these addresses when it no longer connects to that ISP, but in the cases I have been involved with there was always a reasonable time to renumber. Obviously depending on such a grace period is a very dangerous thing to do. You have been warned.