While there's no marketing tactic that can make up for having a crappy product, the notion that you can just email a couple of friends and a product will take off works in maybe 1% of cases, even for good products.
Even if you have something good, the chances you'll be successful without marketing are way worse than the chances you'll be successful as a startup in general (which already suck).
...and if you don't have something good, you'll figure it out a lot faster with marketing than without. With a short runway, like when you're living out of your car or something crazy, figuring that out is pretty important.