For instance, prioritizing on features to build/improve next. I have read support for both sides and can see issues in both. If you give customers what they want it could detract from the core focus of your product. I believe this is called "feature bloat." If you give them what they need they'll realize how valuable your product is to them, but there's also the chance of making a wrong assumption. How do I find out what they need and keep them happy? And is it an uphill battle to convince them that what they really need is more important than what they want?
Always take into consideration what your customers want, even when building "what they really need", because it will give you insight into how best to implement it.
On whether to "give them what they want", it comes down to what % of your customers want something. If 99% of your customers want something, it would probably be best to give it to them. If 5% of your customers want it, don't bother.
If you're just reading posts to a "things I want" forum, then what you may be seeing is the opinion of a loud minority, which will make it look like 99% want something, when really only 2% do.
To accurately assess the % you could actively send out an email poll to all your users asking which of several options they would most want (allow them to choose 1). Embed the poll in the email itself to make it as easy as possible to respond to. Also, if possible embed in the email a screenshot of what each new feature would look like, so that it will be easier for them to see your side of the story about why you think a feature would be "what they actually need". Just have your designer make the screenshots, you don't need to actually have them be programmed and functional.
If you want to discuss this in relation to the unique details of the actual features you're thinking about implementing, let me know,