One of the common problems for design is that people by nature look for similarities rather than differences when faced with something new. When faced with something new, people try to figure out how that thing is like something they already know. This is extremely true in Magic, particularly with game mechanics.
Take flashback for example. When flashback first came out, everyone wanted to look at it as a retread of buyback. Just like buyback, flashback allowed you to play a spell more than once. In addition, both have “back” in their names. Don't laugh, the similarity of names is very relevant in how players perceive things.
The point of this little story is that it is getting harder and harder to do something “different” in Magic because most new ideas have some connection to something we've already done. This was one of the reasons I was so happy with imprint. It was the one new mechanic that couldn't simply be compared to an old mechanic.