The number of people who sign up from places like friends of friends, Betali.st, etc is vanity. It doesn't actually count for anything unless you can turn them in to paying users, which is incredibly unlikely given that they're a completely random bunch of "people interested in startups". It's the difference between being interested in your product and being interested in solving the pain that your product solves. People pay for the latter. People just cost you money if they're the former, albeit not much.

The two metrics that really matter are how many people use your application and how many people pay for your application. You could get a million signups and still fail.

Sorry if this sounds harsh. I learnt this particular lesson the hard way. My advice: work out who your potential users are, who decides to buy the products they use, and market directly to them. Ignore everything else.