The people who initiate interactions with you are probably not a representative sample. The silent majority is an apt term for the bulk of your customers who neither complain nor compliment. When I worked at Yodlee, support requests and posts to our customer forums were heavily skewed toward people with a high degree of technical literacy and financial domain knowledge.
They were constantly seeking to push the limits of how our products could be used. At KISSmetrics, I split my time between absolute beginners and experts (who knew far more about web analytics than I did!). At Yammer, many of our support and feature requests are funneled through a community manager or project manager. Luckily, there is probably consistency in the type of person who reaches out to you.
Once you recognize the direction toward which feedback is biased, you can correct accordingly. When power users or proxy customers such as admins or managers offer feedback, it’s a good idea to investigate how many users it impacts. It’s not uncommon for power users to clamor for improvements to a feature that 90% of users have never even tried. When extremely low-tech or inexperienced customers offer feedback, it’s worth evaluating whether they are viable customers or whether their inexperience is too high a barrier to getting value from your product.