WPP Group’s 24/7 Real Media has formed a B2B online ad network with four media companies:  Nielsen Business Media, Reed Business, McGraw-Hill (NYSE: MHP) and Cygnus Business Media. Although focused on B2B, the BBN, as the ad net is called, is comprised of a number of titles with very different audiences, such as Construction Equipment, Adweek, Aviation Week & Defense Technology and CPA Technology Advisor.  24/7 claims the network has a reach of nearly 10 million monthly uniques across roughly 200 websites. BBN plans to invite other B2B publishers to participate later this year. Derek Reisfield, former CBS exec and MarketWatch co-founder, is chairman of the new venture. Release