People who don't know or care about JWs aren't interested, people who are JWs see it as persecution and validation that there is an enemy out to get them and the WTS is right.
If you see a sign about scientology, how much attention do you really pay to it? (forgetting the JW connection, if you were just average joe)
I feel like these ad campaigns (like lots of advertising) is throwing money away unless you have a very clear and specific campaign, are targeting the right people and can measure the results in order to declare things a success or not.
The seem to feed on the need of people to want to "do something" but personally I think money and effort can be better focused.