Even if, like me, you don’t much care about David Cook, you have to hand it to the hit FOX reality series: It’s putting SMS systems to maximum use, turning them into a giant cash machine. AT&T says the most recent season of “American Idol” show generated 78 million text messages — up from 67 million last season. And an informal poll conducted by the company on its web site reveals that 51 percent of the 416 respondents tended to text more frequently during the “American Idol” season than other times of the year. Another twenty-two percent said they first learned to text message by voting for their favorite “Idol” contestant. Now only if Ma Bell could tell us how much money they are really raking from this tie-up with the talent-based reality show.