As far as I know, there is absolutely no evidence that signature campaign works.
You can measure Facebook ads ROI easily and they work. But you need to spend real fiat money on FBads.
Bounty programs that offer no quantitative results can't be proved to be effective.
When we look on a certain bounty program it would tend to go on all aspects either on signature,social,article,telegra or any other stuffs.We cant really get some evidence that it would or not but we can able to say such thing if the result of ICO would be success or not but considering that this forum do have the biggest traffic specially on crypto related would somehow be a good medium to advertise on compared on FBads which most people didnt even have an idea.