I have been doing some market research. Basically, commercial usability testing is done by the same people who sell web development, in-house. Seeing that they are generally specialists in developing products, they are likely not specialists in finding out what is wrong with their products. And if they were, they would likely not want to deliver genuine results that undermined the appeal of their products.
Only big clients can afford their own in-house experts. Which means everybody else is left to their own judgement regarding the product they are buying. And from swanky agencies, the product comes with the fake (?) guarantee of having been ‘usability-tested’ – by the same people who sell it. Buyer beware. Buyer is likely to be fooled by bling (as suggested by the article in Smashing on ‘Zipf-ing’ your web site rather than re-developing the whole thing, just because some designer says so).
My thinking hat is firmly on.