You don't have to agree...just go to the anem and clownfish forum or go over to rareclownfish.com(where I am a moderater) and ask the question in a new thread. The people on RC to listen to are RedVipe, GSM, myself, and a few other really intelligent people. Over on RCF, listen to CFK(clownfishking), EZHoops, Schlecht, and many other really intelligent breeders.
I strongly disagree with the instinctual part, in a way...I think in the wild it is instinctual, due directly to the fact that if they do not have their anemone, they will die. In a tank, where there is little or no threat of attack, there is not the same necessity as in the wild. Just like a wild dog would rather eat a human than serve him, whereas a domesticated dog is considered man's best friend. Just as tank bred fish are many times more accepting of food.
I think instincts play a part, but I think moreover that environment is the major deciding factor. You see the first picture I posted? Those clowns had that anemone since day one and did not host for 9 months. 9 MONTHS!! I put another WC clown who was already hosting in with them and in 5 minutes they were with him...5 MINUTES!!! Every clown has the ability to host, not everyone will. Look at chrissties clown sitting in a veggie clip? Look at the hundreds of pictures of my clowns hosting a mag3 pump or hosting an overflow box for their "safety net". They just don't know any better...they didn't require an anem, they were never given an anem, they had never known what an anem was. Why would it be expected of the clown to go right into it? They feel more comfortable against a hard black surface becaus that is what they are used to and have seen as their only defense until that point.
I'm not trying to say you're wrong about your ideas, so I'll put it this way. If your clown is hosting an anemone, it can be either a TB or WC clown. If your clown is not hosting an anem or any other like coral, it is 99% chance of being TB(notice I moved the percentage higher, because I am talking only of clowns not hosting). This is obviously an estimate that I have made without significant research, so it could be as low as 80%, but I highly doubt that. Just start going through the threads on either of the above mentioned forums and tell me how many WC clowns are not hosting.
I also doubt the stress idea as a reason for not hosting. I've had a clown that was three times the size of a bleached out 1" BTA that was still hosting. I've had clowns will disease that would still host in anems, even on their last legs. I've had clowns that have hosted literally almost everywhere in my five tanks and have three pairs at the moment(all in separate tanks...would have four, but my allardis didn't make it through QT). I live on the anem and clownfish pages. Not an expert, and I never will be. The best breeders will not even call themselves experts. There really is no expert when it comes to attempting to control life...that's just how it is. I do, however, post and read and learn every day. I read Wilkerson's book, Hoff's book, I've been to ORA twice, I talk to breeder's of every type of clownfish(20/28 recorded species and a few unrecorded hybrids), and at some point hope to make it my life(want to be breeding full time and out of work in 5 years). I'm just trying to pass information on that I feel is correct and that I feel will help these people if they have a problem and wonder why it is.
Guys, you don't have to listen to me. In fact, I hope that you don't. I personally think that the best way to get info is go to a reliable source...luckily we have plenty of them(including the above listed forums) when it comes to clownfish.