Yesterday, I added the following special deal in my service web site :
Help us promoting the site (blogging/tweetting about it, sharing the link in facebook, google+, delicious,… and committing to write a testimonial at the end) and get 5% off in the cost of the basic package I'd be interested in knowing if you think this is a good strategy and, specially, if any of you has tried something similar and whether it worked or not in his/her case.
(I elaborate a little bit more on why/how I decided to go for this option here in case somebody wants to read more)
The thing to worry about is that there's a stigma against bribing, so it may be important to word it in a way that the customer doesn't feel like they're "selling out".
Just a personal gut feeling, but having a "referral" system seems more common and less likely to offend than making a public posting. Wording it in a way that assumes the referrer is doing so because they like the product/service and that the reward is more of an "added bonus" rather than the primary reason for referring will probably also help get the customer in the right mindset (assuming of course that they do love your product/service)
The key is to make sure they feel like they're sharing something that they really feel will help the people they're sharing with, rather than doing so just for a little discount.
For more reading, look into intrinsic vs extrinsic motivation. You want it to be intrinsic.
I recently implemented a similar scheme to my business: refer a friend and get 1 month off free.
Unfortunately, the response rate is abysmal. We, as business owners would imagine an incentive plan like that will make people get on their feet and start referring people but the reality is, most people simply don't bother. In fact, I have more people willing to pay me than actually giving out affiliate links.
The bottom line is, it doesn't hurt to try but do not rely on it as your primary source of traffic.
I think the first step should be to make it super-easy for your happiest customers to share their joy in social media. Make sure that they know that you'd love to have them mention you. I know it may seem obvious, but people sometimes need to be reminded that you'd really appreciate their honest testimonials.
Incentive programs work sometimes -- but mostly they don't. The reason is that once you give someone an economic incentive, they shift into measuring the incentive on an economic basis. And, for the most part, they don't care enough to be monetarily rewarded.
Quick, tactical tip: Build up a strong presence on twitter by sharing really useful content. Ask customers to follow you as part of their "welcome" email. You'll find that some number of these customers will retweet your tweets. It's not the same as an outright endorsement, but it helps.
I would advise you instead to offer a bigger prize, to which people may apply only with friends.
For exapmle a trip, or something related to your product. This way you can reach tons of people because everybody has to share your campaign.
In addition participants may collect 'extra chance points' through offering your campaign to others or by answering to questionnaires.
This way you may collect tons of leads, and customer feedback through questionnaires as well.