As I read it, that analysis (about Mozilla losing money from a Yahoo sale) doesn't factor in the $1 billion payment Mozilla would be owed if they walk away, and is based on the assumption that Mozilla won't be able to make another search deal to replace its revenue with Yahoo. It's probably true that they can't replace 100% of it, but if they partially replace it, and then make up for the shortfall with that billion, that probably takes care of them for many years.