This is a performance art that requires athletic excellence and often strong martial arts basics to evolve to. How many posters here perform traditional forms? How many spar with their hands at their waist? It seems that many here assume that because the XMA guys can trick that they can't defend themselves or spar effectively. Yet, if a MMA/BJJ guy or kickboxer suggests that a TMA guy can't fight because "he wastes all his time doing worthless katas", many positions would change.
I am sure that there are more than a few examples of people out there who are into XMA that only train tricking and really don't put much emphasis on sparring or self defense training. Just as there are a few examples out there of TMA practitioners who only practice their forms and basics and neglect to chunk down the forms and practice them effectively for self defense nor spar. They just run their basics and patterns and consider themselves good martial artists. IMO, these types are basically on the same level, except at least the trickers are likely superior athletes. My guess is that the vast majority of XMA guys as well as TMA practitioners do basically the same thing: they divide up their training time into self defense, sparring, and forms work. Then they modify their techniques and application for which compartment they are working on.
We have a supplimental class at my school for "tricking" and many of the teens and young adults love it. We treat it like dessert and they have to finish their dinner first. In other words, they have to be solid on their curriculum. For us that includes TKD, Muay Thai, BJJ, and Escrima worked into a MMA format (which includes plenty of kickboxing, submission grappling, and NHB sparring). If they are training hard on this and want to come into the tricking class on Saturday morning or stay after class an extra hour on a weeknight and trick, it's fine with me. The ones who do this are mostly among the best fighters (at least for their age) in the school. They'll often work their traditional forms in the same sessions, too. We have a rule that they must attend a minimum of two regular classes a week to attend the tricking class, but this is rarely an issue. From my experience, the kids who want to put the work into this are the ones who want to live at the school anyways with very few exceptions.
When Cung Le wins a MMA fight, he likes to do his signature back flip in celebration. You may notice that he does not try to pull this, a webster or a flashkick against his opponent during the fight. OTOH, the practice he did to get his backflip down did nothing to take away from his ability or effectiveness as a fighter either in san shou or mma. In fact, it might be interesting to note that he is the fighter with the most varied striking arsenal in MMA history and so far has been quite effective with it.