According to George Bilbrey and Stephanie Miller: 

It's actually more important. Many corporate system administrators use the same types of data as Yahoo, Hotmail and other leading ISPs do -- and in many cases, their standards are even tougher.

The reality is that B2B marketers have to work twice as hard as B2C marketers because smaller files make each email address that much more valuable.

Layer in the fact that B2B files are comprised of people's work email addresses, which change frequently (unlike in the consumer world, where people keep their email accounts for 5+ years).

Finally, B2B email is about persuading the subscriber to engage with your content over a long period of time in hopes of building a relationship that will lead to a large sale. There is no unquenchable revenue number to mask poor performance in B2B.

Source: Seven Myths And Two Truths About Inbox Placement