I really think tameness depends on a number of different factors. I believe that temperament is somewhat inherited (something I have recently seen echoed by another very large scale breeder). Runners, in general, are known for being rather skittish. That said, I have some Runners that are extremely calm and friendly, about as close to "lap-ducks" as you can get, despite having been raised in large groups. I do think though that the number raised together does, in general, affect tameness as does the personality of the person doing the raising.
All that aside, I think some generalizations can be made about breeds as well. Some breeds have a higher percentage of outgoing, friendly, calm individuals than others (again, IMHO, and not discounting that there are exceptions to every rule, my tame Runners are an example). In my ducks, my Mini Appleyards have always been some of my most friendly. Now that I am raising Overbergs, I have to say that they are right up there with the Mini Appleyards in friendliness. Also as Annarie said, in my experience, Dutch Hookbills are also quite calm and friendly. Other people have had good experiences with other breeds. Really as others have said, almost any breed can produce a very friendly duck if it is raised with lots of attention.