1. In terms of linguistics, I think that "aiki" is possessive of many activities. Activities may not necessarily be possessive of aiki. Specifically, Aiki-do claims that as an activity it is inclusive of aiki. A person with aiki may express that aiki in a variety of activities. In asserting this claim, even here on Aikiweb we regularly post about the expression of verbal aikido or interpersonal aikido. It is therefore possible to say, "I did aikido this morning" and refer to a non-aikido activity possessed of aiki, such as avoiding a conflict with the ol' ball and chain. The fact the language did not explicitly say "verbal" aikido is more an illustration of poor communication.
2. If the curriculum of aikido defines "aiki" then we have two issues:
First, Probably Ueshiba Sensei would've been doing something like Daito ryu Ueshiba Ha or some such offshoot of the parent curriculum (Daito Ryu) as adopted by a single practitioner. Second, a mixed martial artist who is practicing the technical curriculum of aikido would be practicing aikido; or, practicing Ueshiba ha Daito ryu as mentioned before.
Going back to the original post, Dan says that he sees aikido "all over the place in MMA". Surely, Dan doesn't mean that he sees MMA fighters doing iriminages and nikkyos; he means that he sees certain physical principles at work in MMA. The problem with Dan's statement is that it stretches the definition of aikido to encompass anything in which can be found certain principles ...
Yes. From a principle-based perspective, Aikido shares with many other fighting and body conditioning systems the same core principles we define as "aiki". O Sensei was unselfish of sharing "aiki" and mentioned in several different occassions where he opined that a practictioner he observed was doing aiki. Remember, aikido was neither the only name for what O Sensei taught, nor was it the name O Sensei chose.
I understand aikido has a pressure to define itself and establish itself within the fighting systems. I also understand we are trying to do this with a relatively young curriculum, of which the majority is derived from its parent art. I also understand that a great number of our practitioners are unable to express with clarity and consistency what is aiki. I am not convinced we wish to express our art as a collusion of waza that breaks down when applied within other fighting systems. Rather, I prefer to see it as an expression of aiki, which may be included in the practice of many activities.