Another reason I think the valley works so well is the audience its news outlets have. If you have a great product but can't get news coverage on it, its going to be hard to get growth without a large marketing budget. However, if you're friends with a friend of a Techcrunch write, its much easier to get covered and start to get a core group of users who love your product - and are tech savvy enough to understand that features that don't exist yet will be coming, and they should be patient.
If you try to bootstrap a startup without using SV's media outlets (as would be the case for people who don't have connections to these folks), you're going to have a much harder time.
I think you're vastly over estimating the impact of tech news sites. A decent front page article on techcrunch will get you a couple of thousand visitors, the vast majority of which won't be in your core customer group.
The main advantage of tech news sites is that they're read by potential investors, partners, employees, etc. rather than because they get you users.
You really need to get your early users through graft, tech news coverage won't really help you except in exceptional circumstances.
All depends on the "how". If you make the effort to show that you understand their coverage niche, and make sure that you actually fit into it, and also have (or can package) your story as something newsworthy then go for it.
If you try to bootstrap a startup without using SV's media outlets (as would be the case for people who don't have connections to these folks), you're going to have a much harder time.