Yeah I know the picture is a cargo ship and not a trawler, but you get the idea. TtL uses elements of both AtL and BtL advertising for something that is less of a compromise between the two, and more of a supplemental tactic to use IN ADDITION to the previous two.
Digital Marketing is both casting a wide net and targeting people individually, as it narrows down the prospects in a manner akin to funnels, but is less based on the consumer's choices and more to do with cookies (the web kind, not the yummy kind), which may be covered next week.
360 Marketing is another prime example. It marries the BtL and AtL components to sweep closer to the middle.
The advantages of TtL is not to be underestimated, but unless you are putting effort into one of the bigger two methodologies, go ahead and put TtL on the backburner until you have a strong AtL or BtL, or both, depending on your market, budget, and goals.