Should the Facebook's, Google , Amazon's of this world operate a BGP looking glass ?

Hi All

Should major social networking sites like Facebook,Google and Amazon
operate an IP looking glass ?

i think they should , here is a short justification write-up i did ,
using a real life troubleshooting scenario.

http://www.slideshare.net/peterehiwe/why-major-content-providers-need-an-ip-looking-glass