Tech startups are at least partly to blame for this as well. I've seen so many job postings requiring years of experience in exactly the same combination of technologies the company itself is using. I know it's harder to hire people for their innate abilities than it is for the number of years they've done rails or django or rspec but if you're going to be that inflexible you've got nobody but yourself to blame for t…
Sure, you still have to be able to fit the role they want or replace someone else that can fit the role, but don't overestimate the importance of the requirements.
There might be a case to take them really serious if the job posting really differentiate between what the candidate have to know and what they wish for. Other than that, don't take them too hard.