Here's a random and somewhat unique MEGA SEO issue.
Google webmaster tools reports 160k "not found" URLs on www.microsoft.com. These 160k URLs have about 1.5 million inbound links. :)
Embarking on large-scale 301 redirect mission that could lead nowhere or generate millions of visits. You never know for sure what the impact will be.
What is the street value of 1.5 million links?