—Blog ad revenue to rise 81.5 percent by 2012: Ad spending on blogs will hit $746 million within four years, a 163.6 percent increase over 2007’s $283 million and an 81.5 percent rise over 2008’s projected $411 million, says eMarketer. And while tech blogs are expected to remain strong, expect the PerezHiltons and eco-friendly sites to grab more attention and ad dollars, eMarketer senior analyst Paul Verna said in an interview with paidContent.

—Digitas enters branded content game: The Publicis Groupe interactive ad shop has formed a subsidiary unit that will create and distribute branded entertainment called The Third Act. Digitas won’t say what clients are included in The Third Act, though it is working on a sequel to the Smart Show, a webisode series showcasing concepts like a band that uses typewriters to make music. The first series was sponsored by Holiday Inn Express.

—AOL tapped as Virgin Mobile’s ad provider: Virgin Mobile USA (NYSE: VM) announced today that AOL’s Platform-A (NYSE: TWX) will be the exclusive display advertising and sales partner for its more than 5 million subscribers. As small as that may sound (at least compared to AT&T’s 71.4 million subscribers), this is probably a valuable and highly sought after demographic of youth-oriented 14- to 34-year olds. More details on our sister site mocoNews.

—YouTube hopes for marketers’ buzz:  The latest YouTube analytic tool claims to offer marketers a way to track the next viral hit. YouTube’s new “buzz” algorithm looks at the speed of views, ratings activity and what’s becoming popular, then advertisers can target their ads specifically to videos burning up the buzz rankings. Film studio Lionsgate is the first to sign on.

—Mag sites’ Q1 traffic rises 11.9 percent: Consumer magazine websites are gaining unique visitors, but is that translating into online ad revenue? Still too hard to say. Mag sites averaged 70.7 million monthly uniques in Q108—an 11.9 percent gain over Q107’s 63.2 million uniques, say Magazine Publishers of America and Nielsen Online. As for calculating ad revenue, the MPA, along with other organizations and researchers, have a tough time calculating the online numbers versus print, mainly because no one can agree on a uniform measurement of units similar to that of print mags. Release

—Ad nets are recession proof?: Jupiter Research analyst Emily Riley thinks so—Or at least that ad nets are better positioned than other ad vehicles. In a Jupiter blog post, Riley contends: “Networks represent the most measurable portion of display advertising: therefore it is the most immune to economic downturn.”

—Sun’s not challenging Microsoft, Google: Not that you asked, but Sun Microsystems has no plans to join Microsoft (NSDQ: MSFT), Google (NSDQ: GOOG), AOL and Yahoo (NSDQ: YHOO) in the online ad space. That said, Sun’s new Project Insight will allow developers to install ads into applications they create and while the company feels it could be credible, it has no interest in acquiring companies or taking the other tech-ad players on in that arena.

—Pepsi’s digital renovation: Every two years or so, Pepsi overhauls its site. Last time, its makeover reflected its sponsorship of Nascar. After realizing that consumers were missing its other tie-ins, the soft drink maker decided to go for a more general feel with tabs highlighting music and community sites.