“The Terminal,” the jetset comedy that hits theaters this weekend, is the story of a man trapped in an airport transit lounge, bombarded by ads for American brands and consumer items — Starbucks, Burger King, Hugo Boss, Baja Fresh, Borders Books & Music.Moviegoers might recognize the feeling. The moment they enter a multiplex, they’re bombarded by ads. There are ads in the lobby; they hang from the ceiling; they’re printed on soft-drink containers and popcorn tubs. And lately, there’ve been more and more ads on the bigscreen, playing before the main attraction. Last year, according to the Cinema Advertising Council, $356 million was spent on ads in movie theaters, a 37% jump from the previous year. $315 million of it was for onscreen ads. Those numbers are expected to climb again this year. The result is that a 90-minute feature often comes with a punishing 30-minute reel of trailers and ads. (And if the movie is 2½ hours or longer, it means a pretty long trek for the audience.) This insidious trend reflects a cultural shift in Hollywood. Studios have been weaving product plugs into their films for years, but two decades ago, ads weren’t screened with movie trailers. Today the advertising business is so deeply intertwined with the movie business, it’s grown harder to differentiate between the two. Revlon recently shot a two-minute mini-movie with Halle Berry, Julianne Moore and other spokescelebs that’s screening in movie theaters in top markets. Add to that the tedious ads for Fandango, the Los Angeles Times, and a dozen other consumer brands, and exhibitors may find themselves on dangerous ground. If the number of onscreen ads keep climbing, more moviegoers may skip the multiplex altogether and wait for the DVD.