Falling ratings for Fox's American Idol could have far-reaching reverberations throughout the broadcast and advertising industries, Advertising Age observed today (Monday). The trade publication pointed out that Idol can no longer claim to garner the highest ad rates of any regular telecast. It now shares that status with NBC's Sunday Night Football. Moreover, if ratings continue to fall, advertisers will be forced to figure out how to spread their dollars more in an effort to reach the same number of viewers. And since Fox often requires ad buyers to purchase a package of spots that include other marginal programs, the network will lose a safety net for those programs. Commented AdAge " Idol once walked alone among TV shows. Now it has company."