Which is the exact problem that we're seeing, here. "Oh, I know, I'll just use a segment allocated to somebody else; it's not like they use it!" Aaand...whoops, they do.
It's allocated to "DLA Systems Automation Center," a branch of the US military. The addresses are probably used on NIPRNet/SIPRNet, but not publically routed. (Much like 22.0.0.0/8.)
My personal favorites are 44.128.0.0/16, the explicitly unallocated test network for amateur packet radio to internet gateways, and 100.64.0.0/10, the address range for bidirectional carrier grade NAT.