TV Advertising is still in the Middle Ages. Most channels can target an audience only with guesswork, based on the type of programme broadcast. So, a sitcom such as Girls or the Mindy Project would have ads targeted at women in their 20s and 30s.Websites can profile you through your browser - digital tags known as "cookies" track what you search for, buy, fill in on forms - and sell that information to advertisers who want to target people exactly like you.But when direct competitors to TV such as Facebook or YouTube can drill down to the level of your eating habits, or how much you spend on cleaning products, the vagaries of traditional profiling for TV advertising are simply not going to cut it.But here's the good news if you work in TV: digital set-top boxes put TV on a somewhat more level playing field.Sky Media became the first company in the UK to attempt ads targeted by using data from its set-top box in early 2014. The platform lets brands target specific households, based on their postcode and 90 unique attributes (such as whether they consist only of adults, or if there are children, and approximate income level) from third-party data brokers.Sky has custom segments for more precise targeting, including attributes like pet ownership, occupation and number of cars in a household, which can be bought from data brokers.NBCUniversal, which rolled out its programme in the US this year, uses cable set-top box data, along with credit card, car and other details, to tell advertisers which network, and even which programme on that network, is most likely to reach their target audience.With advanced data-mining technology, the potential for tailoring TV ads on TV is huge.For example, you and your neighbour could both be watching Downton Abbey but would see different ads. If you're environmentally conscious with no kids, you could be shown an electric car. Next door, the couple with young children might be shown an ad for a people-carrier vehicle.Apparently it's working.Sky said an ad for a music album, shown only in homes with children aged five to 11, meant parents were twice as likely to discuss buying the album with their offspring.The next step is to dig in and get more granular, to become more intimate with your target's life and go beyond what his home or neighbourhood say about him. Then the ads will be tailored even more closely.Companies such as the Clypd, in the US, are working on automated tools that swap in the right ad with minimal human intervention.The business model behind television won't survive if it doesn't play the new game - and the currency is data...