Well sure, but it seems to me that if someone is already competent in haskell, or has done some serious networking work on their own, then they've already demon

Well sure, but it seems to me that if someone is already competent in haskell, or has done some serious networking work on their own, then they've already demonstrated that they're worth hiring, and that they'll probably be able to work with whatever you need them to. This is different than looking for someone with 1 year of experience in ruby. The combination of short amount of time and some conflation of ruby and ruby-on-rails in the general populace could lead to a whole lot of incompetent (or inexperienced enough that it would drag the whole project down) devs being attracted to the job. That is not to say that I think that 5 years of experience developing web apps and 3 in ruby is much of a better metric - as you said, (demonstrated) ability, talent, and enthusiasm are much more important than x years in y.