2001:590::/32 announced by both AS4436 (nLayer) and AS4474 (Global Village, no contact in whois, but seems to be nLayer...)

> there is no problem with a prefix being
> announced by more than one ASN.

Bill: have you done any measurement exercises to determine whether this
is, in fact, an issue? Or was your comment above based on the protocol,
rather than deployed implementations of the protocol?

  based on the protocol, not any specific implementation
  thereof.