After making quick work of print newspapers, and the Yellow Pages industry, "The kudzu-like creep of the Internet is about to claim its third analog victim," warns a new report from research firm Borrell Associates. The victim? "The largest and least-read of all print media: Direct mail." "Direct mail has begun spiraling into what we believe is a precipitous decline from which it will never fully recover," Borrell predicts. More specifically, it is projecting a 39% decline for direct mail over the next five years, from $49.7 billion in annual ad spending in 2008 to $29.8 billion by the end of 2013. If Borrell is correct, direct mail will fall from the premiere placeholder for ad revenue to the fourth -- behind the Web, broadcast TV, and newspapers. The downturn is being caused by a perfect storm of worsening economics for printing and delivery and conversely improving economics for competing media, particularly the Internet. In turn, the research firm sees email largely filling the void being left by direct mail. "Email advertising is indeed skyrocketing while its traditional counterpart plummets," Borrell notes. "In fact, last year, email advertising quietly moved to the No. 1 online ad category spot, surpassing all other forms of interactive advertising." Last year, advertisers spent $12.1 billion on email marketing, more than they spent on display/banner advertising or search advertising. Borrell is predicting that email will continue to distance itself from other online advertising formats over the next five years, growing to $15.7 billion and remaining the preferred channel among many marketers. In particular, most of the growth in email marketing will be local, the report forecasts. "We're expecting local e-mail advertising to grow from $848 million in 2008, to $2 billion in 2013, as more small businesses abandon direct mail couponing and promotional orders and turn to a more measurable and less costly medium, e-mail." Still, the report goes on to warn opportunists that email marketing is not without its risks. "Managing large e-mail marketing campaigns require database marketing expertise, a savvy sales force, adequate e-mail management software, familiarity with the rules and regulations and a lot of patience." The declines in direct mail have already begun to register at companies such as Valassis, which owns one of the nation's largest direct-mail businesses. In the first quarter of this year, Valassis' "shared mail" revenue declined 12.7% year-over-year, according to Borrell. Two other direct mailers, meanwhile -- IWCO Direct and Transcontinental USA -- have announced layoffs and facility closings. Of particular note, Borrell credits the rise of coupons online with the demise of direct mail. Last year, for one, 36% of adults picked up a coupon inside a store and used it, compared with 28% just two years ago. About 8% of all adults now report using coupons delivered via email or the broader Web.