Strange practices?

Mon Jun 7 20:50:25 UTC 2010

Has anyone ever heard of a multi-homed enterprise not running bgp with
either of 2 providers, but instead, each provider statically routes a block
to their common customer and also each originates this block in BGP?   One
of the ISP's in this case owns the block and has even provided a letter of
authorization to the other, allowing them to announce it in BGP as well.
  I had personally never heard of this and am curious if this is a common
practice as well as if this would potentially create any problems by 2
Autonomous Systems both originating the same prefix.

Thanks

-Bill