I use annotations in my outros because I know how little kids like to see something and want to watch it, "oh, oh, I want to watch THAT one!". My kids do the same thing. I can't stand cluttered annotations throughout a video though. Annotations for "click like" or "thumbs up for this" while watching a video bug me. Also the invideo things bug me, I'm watching a freakin' video, quit buggin' me with this and that, ha! It's all distracting. I had someone want to 'collaborate' with me, I asked what he had in mind and he said he'd put annotations in his videos to watch mine if I did for his. Uhhhh, no. I don't like to mess up my videos with any annotations during the video, I'm especially not going to do so as billboards to go see yours! To me annotations cheapen videos during watch time unless they serve a rarely unique purpose. After the video is over, go for it in the outro. Just my opinion.