Asking your potential customers to email someone they know with your product information is difficult. In order to provide an incentive for them to do so, you can promise a free gift to the one sending out the email to one of his/her friend. The friend who gets to know your product that his/her friend suggests, and the products mentioned in the email get promoted.
The all-win situation is a great way of marketing your product. Make sure your product is good enough so you won't let the sender down. Also, make sure the gift is worth the sender's effort while you minimize the work of composing the email for the sender to send out.
Use "mailto:" HTML tag to pre-compose the email, set the b.c.c. to yourself so you also get a copy every time the email gets sent out. Then, you process one email a time to deliver the gift to the sender.
Here's an real case example I just received using this approach:
Earlier last week, I was asked to implement an in-memory database similar to Redis (name-value pairs). This post is about code style, algorithmic performance, and thought process. For simplicity's sake, my program to the challenge will receive commands via stdin, and should write appropriate responses to stdout.