It's likely that fans are your most important customers. Unlike normal customers, who may like your products and may purchase again, fans DO like your products and WILL purchase again (assuming you have other products to purchase.) This is great news, but they still need care. Special care, at that.
Fans understand you and your products. They assume you understand them in return. This may or may not be the case, depending on whether or not you stumbled across something they like (luck) or sought them out (strategy.) If you lucked into a successful product that gathered an unexpected fan-base, you better listen extra close to what they say. The chance of that luck holding out is slim. If you've gathered your fan-base with successful strategy, chances are you're more in the ball-park, but you still better listen to what they say. Listen, and act where you can based on Fan input.
Fans, unlike normal customers, have an emotional investment (as well as financial) in your product and/or company. Your success reflects well upon their choices, so they want to see you succeed. They also want more of whatever it is you do, because they like it. It's all good.
If you don't succeed, some fans will turn on you (regular customers don't care enough to), which is part of the emotional aspect of fandom. Working for Wizards, we canceled a lot of products, and it was always rough. When Clout ended, I was totally surprised at the positive reaction from our fans. They were upset, of course, but unlike Wizards fans, Clout fans knew we didn't have choice about whether to keep kicking the Clout horse or letting it go. It's not mindless emotion, gamers are smart people. Treat people right and it you'll be surprised how it comes back to you (often in unexpected ways!)
As I've written before (Viral, Hardcore, or Vanish), if you've sold any games at all, you've always got fans. When you're struggling, all of your customers are fans. They're often the first to arrive (early adopters) and the last to leave. If you have enough fans, you're bound to succeed, even if your game is never a huge hit.
Because fans are so important, and such a powerful part of your customer-base, I think it's essential to communicate to normal customers how they can become fans. Reward them for fan-like behavior. Make being a fan significantly cooler than being just a customer. I don't know how, exactly, it's YOUR game. =-)