NEW YORK — Local mobile advertising will increase 10-fold in the next four years, and will be almost two-thirds of all local online advertising by 2015, according to projections released today at the Local Online Advertising Conference by Borrell Associates.

          Gordon Borrell and Kip Cassino of Borrell said local mobile advertising in the United States last year was about a half-billion dollars, and will reach $1.2 billion this year. By 2015, they said, it will reach $12.5 billion.

          Greg Stuart, of the Mobile Marketing Association, pointed out why. He noted that EBay nearly tripled its gross merchandise sales on mobile during the 2010 holiday season, and quoted author  Chetan Sharma as saying mobile advertising wins out over other media in reach, targeting, engagement, “virality” and transactions. Stuart asked how many of the hundreds of people in the room slept last night with their mobile phones on the nightstand within reach. Most of the hands went up.

          “Daily deals” and mobile seem to be shaping up as the two primary themes of the conference. (More about those themes, and the conference, coming up.)

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          It’s rare to see people from TV groups, radio, newspapers, dot-coms and other media companies all in the same room. They tend to congregate in silos, like the Newspaper Association of America meeting coming up late this month in Dallas or the National Association of Broadcasters and TVB (TV Advertising Bureau) conferences.

          Not so at this conference. Ad media execs of all stripes, sizes and shapes are here. Borrell is expecting 550 attendees, and it’s a helluva strong agenda and a great mix of people. (That attendance figure is slightly murky; Gordon wasn’t sure when I asked last night how many were on-site attendees and how many were attending the streamed-video feed. Judging from the crowd in the room, most of them are on-site. And the streaming video feed is probably drawing a lot of people who are watching with a crowd in the room — meaning 550 may be low.)

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          Katja Riefler, our European director, and I are at the conference, reporting, networking and learning. We’ll post a lot more as the two days unfold.