BizMiles informs:

"We regret to inform you that United Airlines has elected not to participate in bizMiles in the future. If you would like to contact United to voice your opinion on this matter, please go to http://www.ual.com/airline and then go to the Mileage Plus area, click on the Contact Us, and click again on the word "comments" in red at the bottom half of the screen and fill in the form."