Only one customer? There are a couple "consulting" firms in particular around here that use arbitrary space on internal networks. Sometimes a currently-dark IP block is configured, so "it works for us". It gets annoying after a while.
The worst one I've seen so far is Ticketmaster... last month. If you want to sell tickets through them and connect via the network, they require you to have a private, backend connection to them and then require you to route 29.2.0.0/15, 29.4.0.0/15, and 29.6.0.0/16 via that connection. I could be wrong, but somehow, I don't think that they are also known as or have received addresses from: OrgName: DoD Network Information Center OrgID: DNIC Address: 7990 Science Applications Ct Address: M/S CV 50 City: Vienna StateProv: VA PostalCode: 22183-7000 Country: US NetRange: 29.0.0.0 - 29.255.255.255 CIDR: 29.0.0.0/8 NetName: MILX25-TEMP NetHandle: NET-29-0-0-0-1 Parent: NetType: Direct Allocation Comment: Defense Information Systems Agency Comment: Washington, DC 20305-2000 US RegDate: Updated: 2002-10-07 The argument of "what if one of the DoD research groups on campus is trying to connect to this space for classified work?" didn't work... especially given that the blocks aren't in our BGP tables. Alas, my protests failed against the might of our self-funding sports program. Eric :)