My personal opinion: once you see a business offering incentives for customer research (e.g. a starbucks voucher), it's a sign that a few things have gone wrong. And ironically, it likely means they're not very good at genuinely listening to customers.
I've found that there are much better ways to drive engagement and excitement to connect with us as a business, than gift cards or financial rewards. For this reason, at Buffer we have generally not offered any of these sorts of incentives for providing feedback.
That said, to say we offer “no incentive” is really short-changing ourselves. What I mean by that is, if we show that we are an engaged, nimble, actively developed product and we have a team that connects with customers, acts on feedback and circles back to present those improvements we’ve made, then really, we have already built a significant incentive for anyone to connect with us.
This is the ongoing work we must keep up (this work exists everywhere, but especially in Marketing, Advocacy, Product, Social / Community and anywhere we have opportunities to connect directly with customers). To be clear, this isn't easy work. This is the hard work to create a brand and business where people are excited to share their feedback, rather than one where you have to beg for feedback.
And this is what we're fortunate to experience. People who use Buffer are awesome, and generally love to connect with us and share their feedback to improve the product. Many team members who have joined Buffer, especially product designers and product managers who seek customer feedback to do their work, have shared how pleasantly surprised they've been about Buffer customers being responsive and generous with their time in sharing their experience with the product.
If we keep this work up of genuinely engaging, listening and then improving, then it is evident to customers and observers that we care and will act on feedback. As a result they will already have an incentive to connect and contribute, because they have seen evidence that doing so actually can make a difference to the product that they’re using.
In other words, the hack to easily getting great customer research, for free, is to really work with your customers, listen to them, respond to them, make them feel heard and genuinely improve the product based on their input. This is what we strive for every day at Buffer.
We've dabbled with incentives a few times. Each time we did it, I never felt great about it. It took me a while to put a finger on it, but I eventually realized that it felt off because if we have to offer those incentives, then we are falling short in providing the type of experience we strive for (which would obviate the need for those incentives). Offering incentives is now one of those things that I feel like I have to fight for us to avoid as a company, because it's so prevalent and it can be thought of as a best (or at least a normal) practice.