I don't know that it has to be so black and white, though. In some sense, everything we do in a business is a reaction, from starting a business, to adding a feature, to introducing a new product, to exiting the business.
Founding a business: "I started WidgetCo because I really needed a Widget and no one made one that lasted more than two months."? You started a whole company as a reaction.... to a need. And now it's a thriving business.
Adding a feature: "Our customers are really asking for CIFS support. That's coming in version now + 2." You're reacting here... to customer needs. If your customers and potential customers really do all (or most) need that feature, you've expanded your possible footprint. This is how you achieve success.
Introducing a new product: "Sales of our primary product were down and the market was saturated, so we're coming out with a new product". You're reacting here... to your sales pipeline and market conditions.
That's not to say that reacting is always good. Far from it. Adding a feature just because one customer asked for it doesn't mean it will be useful to anyone else (and you may never recoup the cost of building it). Making your product "Web 2.0" just because you read that term in a lot of magazines lately might not make any sense (what does it even mean for your mobile-platform based synchronization product?).
So don't automatically follow your immediate reactions. But don't condemn them either. Give them due consideration as you would any idea, no matter where it came from.