Twitter is testing a subscription plan that charges users $99 a month to automatically promote tweets into strangers' timelines. This wouldn't be a service offered to all: Only those invited would be given the option to bellow out tweets to folks who don't follow them. But at this point, it isn't another tool for big brands to use. It's aimed at users who aren't as Twitter-savvy -- i.e. power users and small businesses -- who would conceivably rather throw money at the social media network than micromanage their account.