"Top" 50 on what basis - what criteria do you want respondents to apply?For example, firms where you'd most like to work, firms you've heard of, firms you'd hire if you were a client, firms with widest reach, firms with broadest range of services, firms with deepest expertise, firms with the best-looking staff?What if you don't think there are 50 worthy of "top" designation, or if there are firms of equal "topness" value according to different criteria?Is this survey methodology representative of the type of "rigour" you peddle to users of the case study site? Not a great advert!