regardless of what has been posted and said, there's always going to be the uninformed or naive novice who tries to put a Powder Blue tang in a 29 gallon. This is the individual who relies solely on inadequate and incompetent LFS sources (not all LFS's are this way, mind you, but the majority are)and perhaps an outdated book or poorly written, obsolete article somewhere.
At least with the internet and discussion groups such as Reefs. org, RC and Aqualink, people can begin to get a grasp on some of the preferred and proven requirements of many of these creatures.
At the very least, the person will get the extremes of each instance, although the low extreme of any reefer who peruses these boards hopefully wouldn't stick a tang in a tank so small and then there are the conservative views that condemn placing such a fish in anything smaller than a 180 gallon.
Hopefully, most newcomers and experienced alike will find a happy medium somewhere in between. It's often far out of one's grasp to be able to muster up enough finances for a full blown 220 gallon reef, and they find themselves at the lower end of the large scale, resting somewhere between a 75 and a 125 (mind you, these are just the common sizes). Which, in my opinion, is a far better circumstance than the former instance. I find myself in that catagory. I still love Tangs and I'll place one in one of these low end large scale tanks (a 90, hopefully soon) but in the end, it'll receive unconditional care, feedings, tankmates and conditions as similiar to their natural environment physically possible in such an enclosed system.
Remember, those here who lurk through these internet posting are a minority; someone is buying all those Tangs, Mandarins and Gonioporas and Cleaner Wrasse you you arriving every week in the LFS in every niche of the country (and world)--and I guarantee you the vast majority haven't even used a search engine to check on the requirements of the animal nor posted a question prior to buying.
So, I'd suspect we're in as good of a boat as any...