Non-geeks find out about technical stuff via their geeky friends and relatives. Firefox is the perfect example.
The only counter examples I can think of are things like Facebook. However, even here, there is no harm in going after techies, unless your product is one of the few that they won't like.
Techies live in a bubble. Let's be frank - most people don't have a clue what IE is, let alone Firefox. Using early adopters as a gateway to a larger market only makes sense if those early adopters are a subset of such a market.
What if you're selling to say: law offices? Doctors? Accountants? HR Directors? None of these markets fit the geek->masses model. You'll fail miserably if you don't target these niches where they already live.
Also, make it easy for existing users to invite new ones. Better still, design your product to be viral/users bring in other users as a natural consequence of using the product (e.g. PayPal, etc.) This sounds obvious but often isn't done well.