When you're sufficiently multi-homed, you can adjust for carrier events as necessary. But one thing that can limit the amount of adjusting you need to do, is support for traffic engineering via BGP communities.
Per
http://www.onesc.net/communities/as4323/ , TWTelecom has some bare-bones TE-communities. Many other carriers provide finer-grained traffic tuning communities.
Oh well, at least TWTelecom supports 4323:666.