For example: Tranny.

If you say that word in any context, your tweet will not show up in many of your followers timelines and if it was a reply it will only show up if you hit show more at least once.

Maybe thats a good thing overall, but I can't help think about the long term effects when the words you can and cannot say can't easily be understood and we end up in some kind of world where only the most sanitized advertiser friendly tweets are the only ones your able to see without having to dig around all the time.