According to a new LinkedIn Research Network/Harris Poll survey of 2,025 adults that was conducted in June, 58% of advertisers say microblogging service Twitter is either very or somewhat effective in promoting products and ideas, and 45% say that Twitter’s use as an ad medium will grow exponentially in the years ahead. But two-thirds of consumers still don’t know much about the service, according to the online survey. Story on BtoB online.