FORTUNE — The technology industry aims to invent the future. But for too many aspiring Silicon Valley workers, it’s their past that’s holding them back.

Who can blame any job-seeker for trying to break into the tech industry? There were 58,000 available Bay Area tech jobs this October, according to job data firm, Wanted Analytics. That’s a slower hiring rate compared with this same time last year, but Bay Area tech hiring still trumps growth in other areas. Coupled with an endless number of high-profile companies like Facebook FB or Twitter TWTR paraded as success stories with humble beginnings, it’s no wonder the Valley is often perceived as the nouveau American Dream.

The problem, according to several job recruiters Fortune spoke with, involves industry outsiders lacking realistic expectations when applying for jobs. To wit, a twentysomething undergrad with a communications degree from a top-tier school might think they have an excellent shot at landing a Google OPEN product manager gig. (They don’t, unless they can answer reported technical questions like, “Write an algorithm that detects meeting conflicts.”)

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“I definitely think people tend to overshoot and be a little too ambitious,” admits Matt Mickiewicz, co-founder of the San Francisco-based Nearly 600 companies, from Pinterest to OpenTable OPEN , rely on Mickiewicz’s online marketplace to recruit new employees. And of the 3,000 to 4,000 new registered users sees every month, roughly 20% are from outside tech, usually gunning for positions like data scientist or product manager, that they are ill-experienced for. Hiring managers never even lay eyes on those applications — the majority are filtered out at the beginning. Says Mickiewicz: “They don’t want to look at resumes that are irrelevant.”

“Entrepreneurialism by itself has become very institutionalized,” argues Neil Warlicht, President of Wahl & Case, a Japan-based boutique recruiting firm with a San Francisco office. To date, it has placed people at tech companies such as Amazon AMZN , Hulu, and Uber. Unless a candidate has a Stanford or Berkeley education and a notable startup name on their resume, they’ll likely hear something like, “So, it’s great you worked for Disney DIS or over at GE GE , but that’s very irrelevant to what we do,” explains Warlicht.

And just because a candidate does have prior tech experience doesn’t mean they’re a shoo-in, either. A startup might not hire an IBM IBM product manager for an in-house position because they don’t seem like a cultural fit or might not excel under the comparatively unstructured workflow of a smaller environment.

That’s not to say it’s impossible for non-tech folks to make the transition. But to compete with MIT grads sporting computer science degrees means candidates must immerse themselves in the tech ecosystem. That includes staying on top of startup news and attending tech meet-ups. It could also mean creating a project for their desired employer — wire frames for a proposed new product, analysis of a potential new business opportunity — and sending it to the CEO or founder.

Says Mickiewicz: “Showing that kind of initiative is highly valued, and you’re much more likely to get a callback.”