[davemel37]

His point is what proof does Google have that this was done by Expedia and not some competitor doing negative SEO?

This doesn't justify the spam, it just makes it much more difficult for Google to detect and penalize due to the mostly natural link profile that Expedia has earned legitimately by building a household brand.

If you had 99% signals saying this is a strong brand worth ranking high, or even only 85% of the signals are positive, and you have a few shady backlinks, wouldn't you give them the benefit of the doubt? Even if you wouldn't can you risk penalizing them without a smoking gun and proof of spam?

The only real question here is why Expedia even bothers with these efforts...Most big brands can get more than enough natural backlinks by launching new programs and services and having all the press pick up the story.